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.

tool/emacs/key.py

@@ -345,7 +345,7 @@ cosmo_kws = frozenset([
   "memcpyesque",
   "nocallback",
   "nodebuginfo",
-  "nodiscard",
+  "dontdiscard",
   "dontinline",
   "noinstrument",
   "nointerpose",
@@ -353,8 +353,7 @@ cosmo_kws = frozenset([
   "noprune",
   "wontreturn",
   "nosideeffect",
-  "nothrow",
-  "nothrow",
+  "dontthrow",
   "null",
   "nullterminated",
   "paramsnonnull",
@@ -408,7 +407,7 @@ cosmo_kws = frozenset([
   "memcpyesque",
   "nocallback",
   "nodebuginfo",
-  "nodiscard",
+  "dontdiscard",
   "dontinline",
   "noinstrument",
   "nointerpose",
@@ -416,8 +415,7 @@ cosmo_kws = frozenset([
   "noprune",
   "wontreturn",
   "nosideeffect",
-  "nothrow",
-  "nothrow",
+  "dontthrow",
   "null",
   "nullterminated",
   "paramsnonnull",