Make more fixes and improvements

- Remove PAGESIZE constant
- Fix realloc() documentation
- Fix ttyname_r() error reporting
- Make forking more reliable on Windows
- Make execvp() a few microseconds faster
- Make system() a few microseconds faster
- Tighten up the socket-related magic numbers
- Loosen restrictions on mmap() offset alignment
- Improve GetProgramExecutableName() with getenv("_")
- Use mkstemp() as basis for mktemp(), tmpfile(), tmpfd()
- Fix flakes in pthread_cancel_test, unix_test, fork_test
- Fix recently introduced futex stack overflow regression
- Let sockets be passed as stdio to subprocesses on Windows
- Improve security of bind() on Windows w/ SO_EXCLUSIVEADDRUSE

libc/calls/sync_file_range.c

@@ -29,7 +29,7 @@
  * @note Linux documentation says this call is "dangerous"; for highest
  *     assurance of data recovery after crash, consider fsync() on both
  *     file and directory
- * @see fsync(), fdatasync(), PAGESIZE
+ * @see fsync(), fdatasync()
  */
 int sync_file_range(int fd, int64_t offset, int64_t bytes, unsigned flags) {
   int rc, olderr;