makepanda: expose save_egg_file/save_egg_data to Python

Closes #582

makepanda/makepanda.py

@@ -4751,7 +4751,7 @@ if not RUNTIME and not PkgSkip("EGG"):
   TargetAdd('p3egg2pg_composite2.obj', opts=OPTS, input='p3egg2pg_composite2.cxx')
 
   OPTS=['DIR:panda/src/egg2pg']
-  IGATEFILES=['load_egg_file.h']
+  IGATEFILES=['load_egg_file.h', 'save_egg_file.h']
   TargetAdd('libp3egg2pg.in', opts=OPTS, input=IGATEFILES)
   TargetAdd('libp3egg2pg.in', opts=['IMOD:panda3d.egg', 'ILIB:libp3egg2pg', 'SRCDIR:panda/src/egg2pg'])