- Fix alias-building & resolving to properly handle optional arguments for command options.
- Add logging for command resolution ('log enable lldb commands')
- Fix alias resolution to properly handle commands that take raw input (resolve the alias, but
  don't muck up the raw arguments).

Net result:  Among other things, 'expr' command can now take strings with escaped characters and
not have the command handling & alias resolution code muck up the escaped characters. E.g.
 'expr printf ("\n\n\tHello there!")' should now work properly.


Not working yet:  Creating aliases with raw input for commands that take raw input.  Working on that.
e.g. 'command alias print_hi expr printf ("\n\tHi!")' does not work yet.

llvm-svn: 121171