Added new x86 assembly for AES.
AES-CBC decrypt only 4 blocks at a time (not 6 or 8) due to reduces
register count.
GCM implementation for AVX2, AVX1 and AESNI only.
Disabled looking for other assembly files for x86.
Some versions of GCC on the Mac will not run the file aes_asm.s through the preprocessor. There are some ifdefs in the file that are included when they shouldn't be. This is not a problem on Linux. Renaming the file to have a capital S extension forces the assembler to run with the preprocessor.