Add cpu / mem / fsz limits to build system

Thanks to all the refactorings we now have the ability to enforce
reasonable limitations on the amount of resources any individual
compile or test can consume. Those limits are currently:

- `-C 8` seconds of 3.1ghz CPU time
- `-M 256mebibytes` of virtual memory
- `-F 100megabyte` limit on file size

Only one file currently needs to exceed these limits:

    o/$(MODE)/third_party/python/Objects/unicodeobject.o: \
        QUOTA += -C16  # overrides cpu limit to 16 seconds

This change introduces a new sizetol() function to LIBC_FMT for parsing
byte or bit size strings with Si unit suffixes. Functions like atoi()
have been rewritten too.

libc/log/checkfail_ndebug.c

@@ -46,5 +46,5 @@ relegated void ___check_fail_ndebug(uint64_t want, uint64_t got,
   __print(bx, uint64toarray_radix16(got, bx));
   __print_string(" (");
   __print(bx, int64toarray_radix10(lasterr, bx));
-  __print_string(")\r\n");
+  __print_string(")\n");
 }