chore, update sxe-compiler macro package

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, introduce secret 4th argument to SXE_CHECK_COMPILER_FLAG, going into AC_LANG_PROGRAM

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, turn off -Wpacked for clang, too much noise

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, work around clang 3.3 bug for good and warn about it

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'bld/clang'

* bld/clang:
  minor, work around clang 3.3 bug for good and warn about it
  minor, turn off -Wpacked for clang, too much noise
  chore, introduce secret 4th argument to SXE_CHECK_COMPILER_FLAG, going into AC_LANG_PROGRAM
  chore, update sxe-compiler macro package