allow OPTIONS to be able to influence dependencies. This is still
experimental [1]
* Teach bsd.gcc.mk about gfortran [2]
* Remove the outdated emulators/linux_base; the new default has been
linux_base-fc4. This will allow the outdated port to be removed [3]
* Add USE_FIREBIRD macros to bsd.database.mk [4]
PR: 93687 [1], 93690 [2], 103184 [3], 103357 [4]
Submitted by: shaun [1], Pedro F. Giffuni <giffunip at asme to org> [2],
gerald [2], thierry [2], vd [3], skv [4]
