Merge pull request #5 in FS/freeswitch from ~KATHLEEN.KING/freeswitch-fork:clang-warnings-werror to master

* commit '1affff9d':
  Fixed a clang-3.5 missing-prototype warning and added doxygen documentation for switch_channel_set_presence_data_vals. #doxygen
  Fixed dead code.
  Fixed trucation of value warning.
  Removed a useless called to abs.
  Removed an autological-pointer-compare from src/switch_utils.c.
  Fixed trucation of value warning.