Make improvements

- More timspec_*() and timeval_*() APIs have been introduced.
- The copyfd() function is now simplified thanks to POSIX rules.
- More Cosmo-specific APIs have been moved behind the COSMO define.
- The setitimer() polyfill for Windows NT is now much higher quality.
- Fixed build error for MODE=aarch64 due to -mstringop-strategy=loop.
- This change introduces `make MODE=nox87 toolchain` which makes it
  possible to build programs using your cosmocc toolchain that don't
  have legacy fpu instructions. This is useful, for example, if you
  want to have a ~22kb tinier blink virtual machine.

third_party/compiler_rt/logbl.c

@@ -26,19 +26,14 @@
 │                                                                              │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/math.h"
+#if !(LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024)
 
 asm(".ident\t\"\\n\\n\
 Musl libc (MIT License)\\n\
 Copyright 2005-2014 Rich Felker, et. al.\"");
 asm(".include \"libc/disclaimer.inc\"");
-/* clang-format off */
+// clang-format off
 
-#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
-long double logbl(long double x)
-{
-	return logb(x);
-}
-#else
 long double logbl(long double x)
 {
 	if (!isfinite(x))
@@ -47,4 +42,5 @@ long double logbl(long double x)
 		return -1/(x*x);
 	return ilogbl(x);
 }
-#endif
+
+#endif /* long double is long */