ch4/stub: remove including mpl.h which is already added in mpidimpl.h

From mpiimpl.h:
pmix.h contains inline functions that calls malloc, calloc, and free,
and it will break with MPL's memory tracing when enabled.
So we need to make sure mpiimpl.h is included before mpl.h.

maint/gen_ch4_api.py

@@ -280,13 +280,11 @@ def dump_func_table_c(c_file, mod):
     print("  --> [%s]" % c_file)
     with open(c_file, "w") as Out:
         dump_copyright(Out)
-        print("#include \"mpl.h\"", file=Out)
-        print("", file=Out)
-        print("MPL_SUPPRESS_OSX_HAS_NO_SYMBOLS_WARNING;", file=Out)
-        print("", file=Out)
         print("#ifndef NETMOD_INLINE", file=Out)
         print("#define NETMOD_DISABLE_INLINES", file=Out)
         print("#include <mpidimpl.h>", file=Out)
+        print("MPL_SUPPRESS_OSX_HAS_NO_SYMBOLS_WARNING;", file=Out)
+        print("", file=Out)
         print("#include \"netmod_inline.h\"", file=Out)
         print("MPIDI_NM_funcs_t MPIDI_NM_%s_funcs = {" % mod, file=Out)
         for a in G.apis: