Apply even more fixups

- Finish cleaning up the stdio unlocked APIs
- Make __cxa_finalize() properly thread safe
- Don't log locks if threads aren't being used
- Add some more mutex guards to places using _mmi
- Specific lock names now appear in the --ftrace logs
- Fix mkdeps.com generating invalid Makefiles sometimes
- Simplify and fix bugs in the test runner infrastructure
- Fix issue where sometimes some functions wouldn't be logged

libc/stdio/ungetc.c

@@ -17,20 +17,15 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/stdio/stdio.h"
-#include "libc/str/str.h"
 
 /**
  * Pushes byte back to stream.
+ * @threadsafe
  */
-int ungetc_unlocked(int c, FILE *f) {
-  if (c == -1) return -1;
-  if (f->beg) {
-    f->buf[--f->beg] = c;
-  } else if (f->end < f->size) {
-    memmove(f->buf + 1, f->buf, f->end++);
-    f->buf[0] = c;
-  } else {
-    return -1;
-  }
-  return c & 255;
+int ungetc(int c, FILE *f) {
+  int rc;
+  flockfile(f);
+  rc = ungetc_unlocked(c, f);
+  funlockfile(f);
+  return rc;
 }