build: Collect all Cflags from pkg-config files.

* m4/acinclude.m4 (OCTAVE_CHECK_LIB, OCTAVE_CHECK_QT_VERSION): Call pkg-config
with "--cflags" instead of "--cflags-only-I" to get all preprocessor flags
(including "-D" and "-F" flags).

Author: mmuetzel

m4/acinclude.m4

@@ -976,7 +976,7 @@ AC_DEFUN([OCTAVE_CHECK_LIB], [
   if test $[ac_octave_]patsubst([$1], [-], [_])_pkg_check = yes; then
     PKG_CHECK_EXISTS(m4_default([$9], [$1]), [
       if test -z "$m4_toupper(patsubst([$1], [-], [_]))_CPPFLAGS"; then
-        m4_toupper(patsubst([$1], [-], [_]))_CPPFLAGS="$($PKG_CONFIG --cflags-only-I m4_default([$9], [$1]) | $SED -e 's/^ *$//')"
+        m4_toupper(patsubst([$1], [-], [_]))_CPPFLAGS="$($PKG_CONFIG --cflags m4_default([$9], [$1]) | $SED -e 's/^ *$//')"
       fi
       if test -z "$m4_toupper(patsubst([$1], [-], [_]))_LDFLAGS"; then
         m4_toupper(patsubst([$1], [-], [_]))_LDFLAGS="$($PKG_CONFIG --libs-only-L m4_default([$9], [$1]) | $SED -e 's/^ *$//')"
@@ -2278,7 +2278,7 @@ AC_DEFUN([OCTAVE_CHECK_QT_VERSION], [AC_MSG_CHECKING([Qt version $1])
 
     if test $build_qt_gui = yes; then
       ## Retrieve Qt compilation and linker flags
-      QT_CPPFLAGS="$($PKG_CONFIG --cflags-only-I $QT_MODULES | $SED -e 's/^ *$//')"
+      QT_CPPFLAGS="$($PKG_CONFIG --cflags $QT_MODULES | $SED -e 's/^ *$//')"
       QT_LDFLAGS="$($PKG_CONFIG --libs-only-L $QT_MODULES | $SED -e 's/^ *$//')"
       QT_LIBS="$($PKG_CONFIG --libs-only-l --libs-only-other $QT_MODULES | $SED -e 's/^ *$//')"