MIR Serialization: Serialize machine instruction names.
This commit implements initial machine instruction serialization. It
serializes machine instruction names. The instructions are represented
using a YAML sequence of string literals and are a part of machine
basic block YAML mapping.
This commit introduces a class called 'MIParser' which will be used to
parse the machine instructions and operands.
Reviewers: Duncan P. N. Exon Smith
Differential Revision: http://reviews.llvm.org/D10481