Make improvements

- This change fixes a bug that allowed unbuffered printf() output (to
  streams like stderr) to be truncated. This regression was introduced
  some time between now and the last release.

- POSIX specifies all functions as thread safe by default. This change
  works towards cleaning up our use of the @threadsafe / @threadunsafe
  documentation annotations to reflect that. The goal is (1) to use
  @threadunsafe to document functions which POSIX say needn't be thread
  safe, and (2) use @threadsafe to document functions that we chose to
  implement as thread safe even though POSIX didn't mandate it.

- Tidy up the clock_gettime() implementation. We're now trying out a
  cleaner approach to system call support that aims to maintain the
  Linux errno convention as long as possible. This also fixes bugs that
  existed previously, where the vDSO errno wasn't being translated
  properly. The gettimeofday() system call is now a wrapper for
  clock_gettime(), which reduces bloat in apps that use both.

- The recently-introduced improvements to the execute bit on Windows has
  had bugs fixed. access(X_OK) on a directory on Windows now succeeds.
  fstat() will now perform the MZ/#! ReadFile() operation correctly.

- Windows.h is no longer included in libc/isystem/, because it confused
  PCRE's build system into thinking Cosmopolitan is a WIN32 platform.
  Cosmo's Windows.h polyfill was never even really that good, since it
  only defines a subset of the subset of WIN32 APIs that Cosmo defines.

- The setlongerjmp() / longerjmp() APIs are removed. While they're nice
  APIs that are superior to the standardized setjmp / longjmp functions,
  they weren't superior enough to not be dead code in the monorepo. If
  you use these APIs, please file an issue and they'll be restored.

- The .com appending magic has now been removed from APE Loader.

libc/fmt/conv.h

@@ -1,16 +1,5 @@
 #ifndef COSMOPOLITAN_LIBC_FMT_CONV_H_
 #define COSMOPOLITAN_LIBC_FMT_CONV_H_
-#include "libc/calls/struct/timespec.h"
-#include "libc/calls/struct/timeval.h"
-#include "libc/nt/struct/filetime.h"
-
-/*───────────────────────────────────────────────────────────────────────────│─╗
-│ cosmopolitan § conversion                                                ─╬─│┼
-╚────────────────────────────────────────────────────────────────────────────│*/
-
-#define MODERNITYSECONDS 11644473600ull
-#define HECTONANOSECONDS 10000000ull
-
 #if !(__ASSEMBLER__ + __LINKER__ + 0)
 COSMOPOLITAN_C_START_
 
@@ -48,52 +37,10 @@ float wcstof(const wchar_t *, wchar_t **);
 double wcstod(const wchar_t *, wchar_t **);
 long double wcstold(const wchar_t *, wchar_t **);
 
-/*───────────────────────────────────────────────────────────────────────────│─╗
-│ cosmopolitan § conversion » time                                         ─╬─│┼
-╚────────────────────────────────────────────────────────────────────────────│*/
-
-int64_t DosDateTimeToUnix(unsigned, unsigned) libcesque nosideeffect;
-struct timeval WindowsTimeToTimeVal(int64_t)
-libcesque nosideeffect;
-struct timespec WindowsTimeToTimeSpec(int64_t)
-libcesque nosideeffect;
-int64_t TimeSpecToWindowsTime(struct timespec) libcesque nosideeffect;
-int64_t TimeValToWindowsTime(struct timeval) libcesque nosideeffect;
-struct timeval WindowsDurationToTimeVal(int64_t)
-libcesque nosideeffect;
-struct timespec WindowsDurationToTimeSpec(int64_t)
-libcesque nosideeffect;
-
-#define MakeFileTime(x)                                        \
-  ({                                                           \
-    int64_t __x = x;                                           \
-    (struct NtFileTime){(uint32_t)__x, (uint32_t)(__x >> 32)}; \
-  })
-
-#define ReadFileTime(t)                     \
-  ({                                        \
-    struct NtFileTime __t = t;              \
-    uint64_t x = __t.dwHighDateTime;        \
-    (int64_t)(x << 32 | __t.dwLowDateTime); \
-  })
-
-#define FileTimeToTimeSpec(x) WindowsTimeToTimeSpec(ReadFileTime(x))
-#define FileTimeToTimeVal(x)  WindowsTimeToTimeVal(ReadFileTime(x))
-#define TimeSpecToFileTime(x) MakeFileTime(TimeSpecToWindowsTime(x))
-#define TimeValToFileTime(x)  MakeFileTime(TimeValToWindowsTime(x))
-
-/*───────────────────────────────────────────────────────────────────────────│─╗
-│ cosmopolitan § conversion » manipulation                                 ─╬─│┼
-╚────────────────────────────────────────────────────────────────────────────│*/
-
 #ifdef _COSMO_SOURCE
 char *stripext(char *);
 char *stripexts(char *);
-#endif
-
-/*───────────────────────────────────────────────────────────────────────────│─╗
-│ cosmopolitan § conversion » computation                                  ─╬─│┼
-╚────────────────────────────────────────────────────────────────────────────│*/
+#endif /* _COSMO_SOURCE */
 
 typedef struct {
   int quot;
@@ -120,10 +67,6 @@ ldiv_t ldiv(long, long) pureconst;
 lldiv_t lldiv(long long, long long) pureconst;
 imaxdiv_t imaxdiv(intmax_t, intmax_t) pureconst;
 
-/*───────────────────────────────────────────────────────────────────────────│─╗
-│ cosmopolitan § conversion » optimizations                                ─╬─│┼
-╚────────────────────────────────────────────────────────────────────────────│*/
-
 #if __STDC_VERSION__ + 0 >= 199901L
 #define div(num, den)   ((div_t){(num) / (den), (num) % (den)})
 #define ldiv(num, den)  ((ldiv_t){(num) / (den), (num) % (den)})