Add detection for PowerPC on Linux.
Add CI configurations for ci-debian-x86.lycus.org.
Overhaul the ABI configuration. Also some related cleanups.

* FLECT_FPABI must now be configured separately from FLECT_ABI.
* FLECT_ABI values completely revamped.
* Flect_FPABI_* values are now defined by the preprocessor.

Slightly related:

* Fixed some target configuration guesstimation results.
* HP-UX added as a supported OS.
* Removed PA-RISC support as it is a dead end architecture.
Update CI configurations with FLECT_FPABI values.
Add CI configurations for ci-debian-ppc.lycus.org.