Adds a new standalone executable "drdisasm" which disassembles hex strings passed as arguments or via stdin. This is useful to evaluate DR's decoder versus other decoders, as well as just being a nice utility. Example usage:
$ clients/bin64/drdisasm -mode x86 62 e2 f5 47 40 41 37 90 62 e2 f5 47 40 41 37 vpmullq {%k7} %zmm17 0x00000dc0(%ecx)[64byte] -> %zmm16 90 nop
Adds a test of drdisasm for all our platforms. Tested on x86, x86_64, arm (and thumb), and aarch64.
Fixes #2987 (closed)