Log Message:
gsm: Update to 1.0.19

Fri Mar 27 15:18:06  2020

	* Release 1.0 Patchlevel 19
	Make it easier to include gsm.h from C++ by wrapping it with macros.
	Throw a #define _POSIX_C_SOURCE 200809L into toast.h to make it
	possible for Linux glibc to just work.
	(Thanks to enh@google.com for the suggestion; errors are mine.)
	Switch from compress/.Z to gzip/.gz