Fix several warnings
Don't refer to static constants as instance vars from const expressions

This is legal, however ICC does not support this syntax.
test: Allow NaN values to differ by sign
cast: Don't use memcpy because it is not inlined by default
Fix missing includes
test: Add tests for several test utilities
Improve XOP detection
Fix several missing casts
cmp: Disable XOP COM instructions on Clang because of codegen bug
dispatch: Improve gcc_linker_bug_workaround
test: Force _vectorcall for x86 MSVC builds

MSVC does not support vectors as value parameters in functions in
x86 mode.
test: Fix 64-bit shift of int
README: Update compiler support