[gimp] m4macros: fixing Makefile.

[Jehan <jehanp src gnome org>]

commit f049267f159cb5923020eaf121e7df9312a9a9ed
Author: Jehan <jehan girinstud io>
Date:   Sun Jul 28 23:08:15 2019 +0200

    m4macros: fixing Makefile.
    
    python3dev.m4 replaces pythondev.m4 and introspection.m4 was added.

 m4macros/Makefile.am | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/m4macros/Makefile.am b/m4macros/Makefile.am
index 40494cc6a0..c79976280a 100644
--- a/m4macros/Makefile.am
+++ b/m4macros/Makefile.am
@@ -10,7 +10,8 @@ uninstalled_m4 = \
        ax_prog_cc_for_build.m4         \
        ax_prog_perl_version.m4         \
        detectcflags.m4                 \
-       pythondev.m4
+       introspection.m4                \
+       python3dev.m4
 
 EXTRA_DIST = $(installed_m4) $(uninstalled_m4)