[Driver] Use libOption with tablegen.

This patch modifies the lldb driver to use libOption for option parsing.
It allows us to decouple option parsing from option processing which is
important when arguments affect initialization. This was previously not
possible because the debugger need to be initialized as some option
interpretation (like the scripting language etc) was handled by the
debugger, rather than in the driver.

Differential revision: https://reviews.llvm.org/D54692

llvm-svn: 347709