Make improvements

This change progresses our AARCH64 support:

- The AARCH64 build and tests are now passing
- Add 128-bit floating-point support to printf()
- Fix clone() so it initializes cosmo's x28 TLS register
- Fix TLS memory layout issue with aarch64 _Alignas vars
- Revamp microbenchmarking tools so they work on aarch64
- Make some subtle improvements to aarch64 crash reporting
- Make kisdangerous() memory checks more accurate on aarch64
- Remove sys_open() since it's not available on Linux AARCH64

This change makes general improvements to Cosmo and Redbean:

- Introduce GetHostIsa() function in Redbean
- You can now feature check using pledge(0, 0)
- You can now feature check using unveil("",0)
- Refactor some more x86-specific asm comments
- Refactor and write docs for some libm functions
- Make the mmap() API behave more similar to Linux
- Fix WIFSIGNALED() which wrongly returned true for zero
- Rename some obscure cosmo keywords from noFOO to dontFOO

libc/intrin/isdebuggerpresent.c

@@ -16,6 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/cp.internal.h"
 #include "libc/calls/syscall-sysv.internal.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
@@ -50,6 +51,7 @@ int IsDebuggerPresent(bool force) {
   if (!PLEDGED(RPATH)) return false;
   res = 0;
   e = errno;
+  BEGIN_CANCELLATION_POINT;
   if ((fd = __sys_openat(AT_FDCWD, "/proc/self/status", O_RDONLY, 0)) >= 0) {
     if ((got = sys_read(fd, buf, sizeof(buf) - 1)) > 0) {
       buf[got] = '\0';
@@ -60,6 +62,7 @@ int IsDebuggerPresent(bool force) {
     }
     sys_close(fd);
   }
+  END_CANCELLATION_POINT;
   errno = e;
   return res;
 }