Summary: minor, add stack to --with-error-checking to turn SSP on

Summary: minor, add stack to --with-error-checking to turn SSP on
Keywords: bldchn diagnostics

This changeset fixes a potential stack bashing in the mapfam permutation
code by inserting proper break statements where they belong.  This could
be one of the reasons of bug #135 and it's yet to be shown that it fixes
anything (other than pleasing coverity).

* configure.ac: add `stack' to the error-checking multiarg

* m4/sxe-compiler.m4: check for -fstack-protector and link with libssp

Signed-off-by: Sebastian Freundt <hroptatyr@fresse.org>