[Core] Fix #182 to some extent

Done with:
 find ./ -name "*.h" -print0 | xargs -0 sed -i "s/#ifndef _\{1,2\}\([A-Z_-]*\)_\(H\|H_\|H__\)/#ifndef MANGOS_H_\1/g"
 and
  find ./ -name "*.h" -print0 | xargs -0 sed -i "s/#define _\{1,2\}\([A-Z_-]*\)_\(H\|H_\|H__\)/#define MANGOS_H_\1/g"
  and some manual checking, compiling.
Merge pull request #191 from lfxgroove/reserved-identifiers

[Core] Fix #182 to some extent