rs6000: Handle Modula-2 in the traceback table

This patch recognises Modula-2 as language for the traceback table,
fixing the problem shown in
https://gcc.gnu.org/ml/gcc-patches/2019-07/msg00848.html .


	* config/rs6000/rs6000-logue.c (rs6000_output_function_epilogue):
	Handle Modula-2.

From-SVN: r273411