Fix syntax highlighting of $ in Emacs

[Magnus Henoch]

This patch fixes Emacs syntax highlighting of the dollar sign in two
cases, namely for strings ending with a dollar sign and an escaped
double quote as a character constant:

-vsn("$Revision: 42 $").

foo() ->
    $\".

These combinations used to cause the syntax highlighter to believe that
the following code is part of a string.

git fetch git://github.com/legoscia/otp.git dollar_font_lock

-- 
Magnus Henoch, magnus@REDACTED
  Erlang Solutions
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