Allow enabling of dummy error_strerror() to support some use-cases

Enable a dummy error function to make use of error_strerror() in
third party libraries easier.

Disable if you run into name conflicts and want to really remove the
error_strerror()
(cherry picked from commit 8fe40dcd7d3b46193f74032361efb674112ee9e5)

Conflicts:
	ChangeLog
	programs/util/strerror.c
diff --git a/ChangeLog b/ChangeLog
index 1d39489..6753726 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 PolarSSL ChangeLog
 
+= Branch 1.1
+Changes
+   * Allow enabling of dummy error_strerror() to support some use-cases
+
 = Version 1.1.5 released on 2013-01-16
 Bugfix
    * Fixed MPI assembly for SPARC64 platform