options/posix: add some more feature test macros

os-test shows we don't define these even though we support everything needed for them.

Author: ElectrodeYT

options/posix/include/unistd.h

@@ -37,6 +37,17 @@ extern "C" {
 #define _POSIX_THREAD_SAFE_FUNCTIONS _POSIX_VERSION
 #define _POSIX_MONOTONIC_CLOCK 0
 
+// mmap, msync, munmap
+#define _POSIX_MAPPED_FILES _POSIX_VERSION
+// mlockall, munlockall
+#define _POSIX_MEMLOCK _POSIX_VERSION
+// mlock, munlock
+#define _POSIX_MEMLOCK_RANGE _POSIX_VERSION
+// mmap, munmap, shm_open, shm_unlink
+#define _POSIX_SHARED_MEMORY_OBJECTS _POSIX_VERSION
+// open, msync, fsync, fdatasync
+#define _POSIX_SYNCHRONIZED_IO _POSIX_VERSION
+
 /* MISSING: additional _POSIX and _XOPEN feature macros */
 /* MISSING: _POSIX_TIMESTAMP_RESOLUTION and _POSIX2_SYMLINKS */