gdb: ensure extension_language_python is always defined

In this commit:

  commit c6a6aad52d
  Date:   Mon Oct 25 17:25:45 2021 +0100

      gdb/python: make some global variables static

building without Python was broken.  The extension_language_python
global was moved from being always defined, to only being defined when
the HAVE_PYTHON macro was defined.  As a consequence, building without
Python support would result in errors like:

  /usr/bin/ld: extension.o:(.rodata+0x120): undefined reference to `extension_language_python'

This commit fixes the problem by moving the definition of
extension_language_python outside of the HAVE_PYTHON macro protection.

gdb/python/python.c

@@ -164,6 +164,8 @@ static const struct extension_language_ops python_extension_ops =
   gdbpy_colorize,
 };
 
+#endif /* HAVE_PYTHON */
+
 /* The main struct describing GDB's interface to the Python
    extension language.  */
 const struct extension_language_defn extension_language_python =
@@ -186,6 +188,8 @@ const struct extension_language_defn extension_language_python =
 #endif
 };
 
+#ifdef HAVE_PYTHON
+
 /* Architecture and language to be used in callbacks from
    the Python interpreter.  */
 struct gdbarch *python_gdbarch;