Make array object extern

Make array object extern

Compiling python.c in C++ mode, we get:

  ...src/gdb/python/python.c: At global scope:
  ...src/gdb/python/python.c:106:31: error: storage size of ‘GdbMethods’ isn’t known
   static PyMethodDef GdbMethods[];
				 ^

Fix it by making the affected array objects extern.

gdb/ChangeLog:
2015-02-27  Pedro Alves  <palves@redhat.com>

	* python/python.c (GdbMethods): Rename to ...
	(python_GdbMethods): ... this and make extern.
	(GdbModuleDef): Rename to ...
	(python_GdbModuleDef): ... this and make extern.