gcc-changelog: fix parse_git_name_status for renames.

gcc-changelog: fix parse_git_name_status for renames.

Renamed files are listed in the following format:

M	gcc/ada/Makefile.rtl
M	gcc/ada/impunit.adb
R097	gcc/ada/libgnat/s-atopar.adb	gcc/ada/libgnat/s-aoinar.adb
R095	gcc/ada/libgnat/s-atopar.ads	gcc/ada/libgnat/s-aoinar.ads
A	gcc/ada/libgnat/s-aomoar.adb
A	gcc/ada/libgnat/s-aomoar.ads

So 'R' is followed by a percentage number.

contrib/ChangeLog:

	* gcc-changelog/git_commit.py: Fix renamed files in
	parse_git_name_status.
	* gcc-changelog/test_email.py: Add test for it.