[binutils-gdb] Add -Wimplicit-fallthrough

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT 85e26832a019ffc00dad9f1eb7e670b85c8eca7f ***

Author: Tom Tromey <tom@tromey.com>
Branch: master
Commit: 85e26832a019ffc00dad9f1eb7e670b85c8eca7f

Add -Wimplicit-fallthrough

This adds -Wimplicit-fallthrough to the set of default warnings.

2018-05-04  Tom Tromey  <tom@tromey.com>

	* configure: Rebuild.
	* warning.m4 (AM_GDB_WARNINGS): Add -Wimplicit-fallthrough.

gdbserver/ChangeLog
2018-05-04  Tom Tromey  <tom@tromey.com>

	* configure: Rebuild.