* acinclude.m4: only turn on FORTIFY_SOURCE if it won't anger gcc

Following libvirt commits cf9bced0 and 1c2edf0f
* .gitignore: ignore test result files (*.trs)
Shellvars: ignore network configs with ! in their name

NetworkManager would write such files, but that leads to problems during
aug_init, as the attempt to create the node
/augeas/files/etc/sysconfig/network-scripts/FILE!NAME will fail as that is
not a valid path expression
augparse: add --trace option

Using --trace will print the filenames of all modules that are loaded.