CPPFLAGS should contain -I and -D flags.
This also has the effect of fixing the build of this module.
mod_LTLIBRARIES = mod_h323.la
mod_h323_la_SOURCES = mod_h323.cpp
-mod_h323_la_CFLAGS = $(AM_CFLAGS) -I$(PTLIBDIR) -I/usr/include/openh323 -I. -DPTRACING=1 -D_REENTRANT -fno-exceptions
+mod_h323_la_CFLAGS = $(AM_CFLAGS) -fno-exceptions
+mod_h323_la_CPPFLAGS = $(AM_CPPFLAGS) -I$(PTLIBDIR) -I/usr/include/openh323 -I. -DPTRACING=1 -D_REENTRANT
+mod_h323_la_CPPFLAGS += -DPTRACING=1 -D_REENTRANT
mod_h323_la_LIBADD = $(switch_builddir)/libfreeswitch.la
mod_h323_la_LDFLAGS = -avoid-version -module -no-undefined -shared -L/usr/lib -lopenh323 -lpt -lrt