BaseTools: Add ConvertMasmToNasm.py script

This script is intended to assist with MASM to NASM syntax
conversions.

The output should be manually inspected and adjusted as needed, since
this script does not provide a perfect conversion.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>