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/build/lib/elfwriter.h

@@ -55,7 +55,7 @@ struct ElfWriter {
   struct Interner *shstrtab;
 };
 
-struct ElfWriter *elfwriter_open(const char *, int) nodiscard;
+struct ElfWriter *elfwriter_open(const char *, int) dontdiscard;
 void elfwriter_cargoculting(struct ElfWriter *);
 void elfwriter_close(struct ElfWriter *);
 void elfwriter_align(struct ElfWriter *, size_t, size_t);

tool/build/lib/machine.h

@@ -169,7 +169,7 @@ struct Machine {
   void (*onlongbranch)(struct Machine *);
 } forcealign(64);
 
-struct Machine *NewMachine(void) nodiscard;
+struct Machine *NewMachine(void) dontdiscard;
 void FreeMachine(struct Machine *);
 void ResetMem(struct Machine *);
 void ResetCpu(struct Machine *);
@@ -181,7 +181,7 @@ long AllocateLinearPage(struct Machine *);
 long AllocateLinearPageRaw(struct Machine *);
 int ReserveReal(struct Machine *, size_t);
 int ReserveVirtual(struct Machine *, int64_t, size_t, uint64_t);
-char *FormatPml4t(struct Machine *) nodiscard;
+char *FormatPml4t(struct Machine *) dontdiscard;
 int64_t FindVirtual(struct Machine *, int64_t, size_t);
 int FreeVirtual(struct Machine *, int64_t, size_t);
 

tool/build/lib/pty.h

@@ -65,7 +65,7 @@ struct Pty {
 };
 
 void FreePty(struct Pty *);
-struct Pty *NewPty(void) nodiscard;
+struct Pty *NewPty(void) dontdiscard;
 void PtyResize(struct Pty *, int, int);
 ssize_t PtyRead(struct Pty *, void *, size_t);
 ssize_t PtyWrite(struct Pty *, const void *, size_t);