Import C++ Standard Template Library

You can now use the hardest fastest and most dangerous language there is
with Cosmopolitan. So far about 75% of LLVM libcxx has been added. A few
breaking changes needed to be made to help this go smoothly.

- Rename nothrow to dontthrow
- Rename nodiscard to dontdiscard
- Add some libm functions, e.g. lgamma, nan, etc.
- Change intmax_t from int128 to int64 like everything else
- Introduce %jjd formatting directive for int128_t
- Introduce strtoi128(), strtou128(), etc.
- Rename bsrmax() to bsr128()

Some of the templates that should be working currently are std::vector,
std::string, std::map, std::set, std::deque, etc.

test/libc/xed/x86ild_lib.c

@@ -25,7 +25,7 @@
 #include "test/libc/xed/lib.h"
 #include "third_party/xed/x86.h"
 
-testonly nodiscard uint8_t *unbingx86op(const char16_t *codez) {
+testonly dontdiscard uint8_t *unbingx86op(const char16_t *codez) {
   size_t len;
   len = strlen16(codez);
   return unbingbuf(xmalloc(ROUNDUP(len, 16)), len, codez, 0x90);