Merge remote-tracking branch 'github_caclark_geeqie/master'

* github_caclark_geeqie/master:
  Add "-Werror -Wno-error=" to the default CFLAGS.
  Fix GCC and Clang compile warnings.

diff --cc src/layout.c
Simple merge

diff --cc src/layout_util.c
Simple merge

diff --cc src/preferences.c
Simple merge

diff --cc src/typedefs.h
Simple merge