Don't compile files generated by gengetopt with -Wall.

gcc-4.6.0 spits out lots of warningns of the form

	cmdline/recv.cmdline.c:439:9: warning: variable 'stop_char' set but not used [-Wunused-but-set-variable]

Silence these warnings by moving -Wall to the set of debug flags
which are not used for compiling *.cmdline.c files.

For some versions of gcc, including gcc-3.3.3 which is still supported,
the -Wformat-security and -Wmissing-format-attribute options depend on
-Wformat, which is turned on by -Wall, so we have to move these options
also to the DEBUG_CPPFLAGS.