[llvm-objdump] Support detection of feature bits from the object and implement this for Mips.
The Mips implementation only covers the feature bits described by the ELF
e_flags so far. Mips stores additional feature bits such as MSA in the
Also fixed a small bug this revealed where microMIPS wouldn't add the
EF_MIPS_MICROMIPS flag when using -filetype=obj.
Reviewers: echristo, rafael
Subscribers: rafael, mehdi_amini, dsanders, sdardis, llvm-commits
Differential Revision: http://reviews.llvm.org/D21125