[llvm-readobj] Accept (and ignore) --wide (-W) command-line switch

Accept and ignore --wide/-W. In GNU readelf this switch is
necessary to get the output format that's consistent between
32-bit and 64-bit targets. llvm-readobj always produces that
output format.

Patch by Roland McGrath

Differential Revision: https://reviews.llvm.org/D33873

llvm-svn: 308396