Note change in signgam implementation from upstream.
Fix asm2 compilation where __toread was used.
Replace implementation of warn*/err*.

This eliminates a large number of warnings about incompatible function pointer
casts when compiling for asm.js.
stdlib/strtod.c is no longer used.

This has been replaced with code from musl.
Replace getopt_long with musl version.
Move err/warn/etc from libc to libcextra.
Expand aliases for strto*_l() to short functions.

This removes warnings about incompatible pointer types in asm2 mode.
Bump version.
Merge pull request #2009 from waywardmonkeys/updates2

Updates2