Remove unused file.
Let libc.symbols use same symbol format as libcxx.

This is just the output of 'llvm-nm -extern-only -defined-only'.
Add musl wchar function implementations.
Add musl multibyte function implementations.
Move wchar,mb stuff to libcextra.
Bump version.
Add a readme giving the date / revision of these sources.
Clean up libc / libcxx build infrastructure.

This creates a couple of additional methods to reduce copy/paste
and make things a bit easier to follow.
Remove 'if()' branches from i64 add and subtract code.
Restore the overflow check to llvm_uadd_with_overflow_i64 to account for the case 0xFFFFFFFFFFFFFFFF + 0x0000000100000001 == 0x0000000100000000.
Improve test/cases/uadd_overflow_64_ta2.ll to check that the tricky addition case 0xFFFFFFFFFFFFFFFF + 0x0000000100000001 is handled correctly.
add a define of __EMSCRIPTEN__
fix memory corruption in setjmp/asm.js; fixes #1087
remove UNRESOLVED_AS_DEAD since it doesn't work
emit coercion on i64 math call return values
coerce output of bitshift*
properly coerce setjmp helpers
add missing coercion in strcat
add coercion in strncasecmp
Merge pull request #1063 from waywardmonkeys/musl-libc

Add wchar and multibyte libc functions