qa script process fixups

"make clean all -jN" completely screws up our BUILT_SOURCES
dependencies (which is only obvious if the repo is starting from a
completely clean state and thus lacking initial dependency info).
Splitting it up into two commands fixes it.
Switch log_fatal from abort() to _exit()

It was moved from exit() to abort() in 1f266bbd.  I like the idea
of trying to avoid cleanup tasks on exit, but abort() is just too
messy and gives the impression it's the result of a software bug.
libgdmaps: refactor to avoid dclist signedness issues/confusion
libgdmaps: switch city_auto_map interface to double degrees

This moves the details of converting from the internal geoip1
integer format (and handling the "0,0 means undefined" case)
into gdgeoip.c where it belongs. geoip2 will give us the data
directly as double degrees.
Add GeoIP2 database support to plugin_geoip

This adds an optional build-time dependency on libmaxminddb.  Note
this commit lacks tests for the new code, which will come a little
later.  This has had only very limited, manual testing so far:
Use At Your Own Risk!