Revert "libfabric: add missing header file"

That wasn't a missing header file; in fact, it should have been
.gitignored!

This reverts commit 35bf5fc60c4970f988e80c7101fd5f27a22ea790.
gitignore: even more regexp ignores

Simple regexps to always ignore the hwloc/libevent stuff, regardless
of their specific version.

Yay regexps!