[dwarfdump] Add verbose output for .debug-line section

This patch adds dumping of line table instructions as well as the final
state at each specified pc value in verbose mode. This is essentially
the same as the default in Darwin's dwarfdump. Dumping the actual line
table opcodes can be particularly useful for something like debugging a
bad `.debug_line` section.

Differential revision: https://reviews.llvm.org/D37971

llvm-svn: 313910