Make fixes and improvements

- Fix handling of precision in hex float formatting
- Enhance the cocmd interpreter for system() and popen()
- Manually ran the Lua unit tests, which are now passing
- Let stdio i/o operations happen when file is in error state
- We're now saving and restoring xmm in ftrace out of paranoia

libc/str/str.h

@@ -203,6 +203,7 @@ typedef const int *wctrans_t;
 wctrans_t wctrans(const char *);
 wint_t towctrans(wint_t, wctrans_t);
 
+int getsubopt(char **, char *const *, char **) paramsnonnull();
 char *strsignal(int) returnsnonnull libcesque;
 char *strsignal_r(int, char[hasatleast 15]) returnsnonnull libcesque;
 char *strerror(int) returnsnonnull dontthrow nocallback;