Fix XNU / FreeBSD / OpenBSD / RHEL5 / NT bugs

For the first time ever, all tests in this codebase now pass, when
run automatically on macos, freebsd, openbsd, rhel5, rhel7, alpine
and windows via the network using the runit and runitd build tools

- Fix vfork exec path etc.
- Add XNU opendir() support
- Add OpenBSD opendir() support
- Add Linux history to syscalls.sh
- Use copy_file_range on FreeBSD 13+
- Fix system calls with 7+ arguments
- Fix Windows with greater than 16 FDs
- Fix RUNIT.COM and RUNITD.COM flakiness
- Fix OpenBSD munmap() when files are mapped
- Fix long double so it's actually long on Windows
- Fix OpenBSD truncate() and ftruncate() thunk typo
- Let Windows fcntl() be used on socket files descriptors
- Fix Windows fstat() which had an accidental printf statement
- Fix RHEL5 CLOCK_MONOTONIC by not aliasing to CLOCK_MONOTONIC_RAW

This is wonderful. I never could have dreamed it would be possible
to get it working so well on so many platforms with tiny binaries.

Fixes #31
Fixes #25
Fixes #14

libc/calls/internal.h

@@ -9,6 +9,7 @@
 #include "libc/dce.h"
 #include "libc/limits.h"
 #include "libc/macros.h"
+#include "libc/nt/struct/ntexceptionpointers.h"
 #include "libc/nt/struct/securityattributes.h"
 #include "libc/nt/struct/startupinfo.h"
 #include "libc/nt/struct/systeminfo.h"
@@ -37,7 +38,7 @@ struct IoctlPtmGet {
 };
 
 struct Fds {
-  size_t f;  // arbitrary free slot start search index
+  size_t f;  // lowest free slot
   size_t n;  // monotonic capacity
   struct Fd {
     int64_t handle;
@@ -59,6 +60,7 @@ struct Fds {
 
 extern const struct Fd kEmptyFd;
 
+hidden extern int __vforked;
 hidden extern int g_sighandrvas[NSIG];
 hidden extern struct Fds g_fds;
 hidden extern struct NtSystemInfo g_ntsysteminfo;
@@ -91,6 +93,7 @@ forceinline size_t clampio(size_t size) {
 
 char *getcwd$sysv(char *, u64) hidden;
 i32 __dup3$sysv(i32, i32, i32) hidden;
+i32 __execve$sysv(const char *, char *const[], char *const[]) hidden;
 i32 __fstat$sysv(i32, struct stat *) hidden;
 i32 __fstatat$sysv(i32, const char *, struct stat *, i32) hidden;
 i32 __pipe2$sysv(i32[hasatleast 2], u32) hidden;
@@ -119,7 +122,8 @@ i32 fsync$sysv(i32) hidden;
 i32 ftruncate$sysv(i32, i64) hidden;
 i32 futimes$sysv(i32, const struct timeval *) hidden;
 i32 futimesat$sysv(i32, const char *, const struct timeval *) hidden;
-i32 getdents(i32, char *, u32) hidden;
+i32 getdents(i32, char *, u32, i64 *) hidden;
+i32 getitimer$sysv(i32, struct itimerval *) hidden;
 i32 getppid$sysv(void) hidden;
 i32 getpriority$sysv(i32, u32) hidden;
 i32 getrlimit$sysv(i32, struct rlimit *) hidden;
@@ -150,7 +154,10 @@ i32 sched_setaffinity$sysv(i32, u64, const void *) hidden;
 i32 sched_yield$sysv(void) hidden;
 i32 setitimer$sysv(i32, const struct itimerval *, struct itimerval *) hidden;
 i32 setpriority$sysv(i32, u32, i32) hidden;
+i32 setresgid$sysv(uint32_t, uint32_t, uint32_t) hidden;
+i32 setresuid$sysv(uint32_t, uint32_t, uint32_t) hidden;
 i32 setrlimit$sysv(i32, const struct rlimit *) hidden;
+i32 setsid$sysv(void) hidden;
 i32 sigaction$sysv(i32, const void *, void *, i64) hidden;
 i32 sigprocmask$sysv(i32, const sigset *, sigset *, u64) hidden;
 i32 sigsuspend$sysv(const sigset *, u64) hidden;
@@ -169,6 +176,7 @@ i64 copy_file_range$sysv(i32, long *, i32, long *, u64, u32) hidden;
 i64 getrandom$sysv(void *, u64, u32) hidden;
 i64 pread$sysv(i32, void *, u64, i64) hidden;
 i64 preadv$sysv(i32, struct iovec *, i32, i64) hidden;
+i64 ptrace$sysv(int, i32, void *, void *) hidden;
 i64 pwrite$sysv(i32, const void *, u64, i64) hidden;
 i64 pwritev$sysv(i32, const struct iovec *, i32, i64) hidden;
 i64 read$sysv(i32, void *, u64) hidden;
@@ -176,10 +184,6 @@ i64 sendfile$sysv(i32, i32, i64 *, u64) hidden;
 i64 splice$sysv(i32, i64 *, i32, i64 *, u64, u32) hidden;
 i64 vmsplice$sysv(i32, const struct iovec *, i64, u32) hidden;
 i64 write$sysv(i32, const void *, u64) hidden;
-int getitimer$sysv(i32, struct itimerval *) hidden;
-int setresgid$sysv(uint32_t, uint32_t, uint32_t) hidden;
-int setresuid$sysv(uint32_t, uint32_t, uint32_t) hidden;
-int setsid$sysv(void) hidden;
 u32 getgid$sysv(void) hidden;
 u32 getpid$sysv(void) hidden;
 u32 getsid$sysv(int) hidden;
@@ -248,6 +252,8 @@ int utimensat$nt(int, const char *, const struct timespec *, int) hidden;
 int getrusage$nt(int, struct rusage *) hidden;
 int setitimer$nt(int, const struct itimerval *, struct itimerval *) hidden;
 int nanosleep$nt(const struct timespec *, struct timespec *) hidden;
+int faccessat$nt(int, const char *, int, uint32_t) hidden;
+int execve$nt(const char *, char *const[], char *const[]) hidden;
 
 /*───────────────────────────────────────────────────────────────────────────│─╗
 │ cosmopolitan § syscalls » windows nt » support                           ─╬─│┼
@@ -266,6 +272,7 @@ int ntaccesscheck(const char16_t *, u32) paramsnonnull() hidden;
 int64_t __winerr(void) nocallback privileged;
 int __mkntpath(const char *, char16_t[hasatleast PATH_MAX - 16]) hidden;
 int __mkntpath2(const char *, char16_t[hasatleast PATH_MAX - 16], int) hidden;
+unsigned __wincrash$nt(struct NtExceptionPointers *);
 
 /*───────────────────────────────────────────────────────────────────────────│─╗
 │ cosmopolitan § syscalls » metal                                          ─╬─│┼