Initial port of lldb debugging mode to run under Emacs's Grand Unified Debugger (gud.el).

The gud.el is modified from 22.3.1 version to add lldb stuffs, the gud-diffs.txt is the
diff file.

lldb-gud-window.tiff is a screen capture of Aquamacs 2.1 (which has 23.2.50.1) after
loading this modified gud.el, changing directory to test/conditional_break, and then
'M-x lldb' with the a.out file.

llvm-svn: 117748