[scan-view] replace deprecated optparse with argparse

Summary: scan-view migrated from optparse deprecated Python module to its replacement (argparse) and resolved few conflicts with pep8

Reviewers: ddunbar, aaron.ballman, dcoughlin, jroelofs, zaks.anna

Subscribers: cfe-commits

Patch by Kirill Bobyrev!

Differential Revision: http://reviews.llvm.org/D15370

llvm-svn: 256150