Add -D_FORTIFY_SOURCE=2 to CFLAGS if possible.

Some distros now add -D_FORTIFY_SOURCE=2 by default and we have missed
some issues in the past caught by it. Add it to CFLAGS if possible.
The configure check will make sure that it doesn't conflict with any
other CFLAGS already defined.

Signed-off-by: Mark Wielaard <mark@klomp.org>
2 files changed