Declare indentation options as "safe" in erlang-mode for Emacs

Emacs has a facility for setting options on a per-file basis based on
comments in the source file.  By default, all options are considered
"unsafe", and the user is queried before the variable is set.  This
patch declares the variables erlang-indent-level, erlang-indent-guard
and erlang-argument-indent to be safe, if the value specified in the
source file is valid.

Such declarations usually look like this:

%% -*- erlang-indent-level: 2 -*-

and appear on the first line of the file.

1 files changed, 3 insertions, 0 deletions

diff --git a/lib/tools/emacs/erlang.el b/lib/tools/emacs/erlang.el
index ed825a298f..17b093ee34 100644
--- a/lib/tools/emacs/erlang.el
+++ b/lib/tools/emacs/erlang.el
@@ -466,14 +466,17 @@ To activate the workaround, place the following in your `~/.emacs' file:
 
 (defvar erlang-indent-level 4
   "*Indentation of Erlang calls/clauses within blocks.")
+(put 'erlang-indent-level 'safe-local-variable 'integerp)
 
 (defvar erlang-indent-guard 2
   "*Indentation of Erlang guards.")
+(put 'erlang-indent-guard 'safe-local-variable 'integerp)
 
 (defvar erlang-argument-indent 2
   "*Indentation of the first argument in a function call.
 When nil, indent to the column after the `(' of the
 function.")
+(put 'erlang-argument-indent 'safe-local-variable '(lambda (val) (or (null val) (integerp val))))
 
 (defvar erlang-tab-always-indent t
   "*Non-nil means TAB in Erlang mode should always re-indent the current line,