std::libc: Remove TCHAR types
std::libc: Simplify win32/win64 type definitions
std: Fix transmute error on win64
llvm: Disable pthreads on mingw-w64 platforms
std::rt: Fix record_stack_bounds on win64
std::rt: Fix crate_map on Win64
auto merge of #10631 : klutzy/rust/win-fixes, r=alexcrichton

This patchset fixes some parts broken on Win64.

This also adds `--disable-pthreads` flags to llvm on mingw-w64 archs (both 32-bit and 64-bit, not mingw) due to bad performance. See #8996 for discussion.