[emacs] llvm-mode: fix parens, font-lock i*

In llvm-mode, with electric-pair-mode turned on, typing a literal '['
would print out '[[', and '(' would print a '(('. This was a very
annoying bug caused by overzealous syntax-table entries: the parens are
already part of the '(' and ')' class by default. Fix this.

While at it, notice that i32, i64, i1 etc. are not font-locked despite a
clear intent to do so. The issue is that regexp-opt doesn't accept
regular expressions. So, spell out the common literal integers with
different widths.

Differential Revision: http://reviews.llvm.org/D7036

llvm-svn: 226931