[Debian GNUstep maintainers] Please give back gnustep-base/1.19.3-1 on hppa

[Yavor Doganov]

For some reason, gnustep-base reliably failed to build (7 times) on
hppa between Nov 18/Dec 1 due to inability to satisfy Build-Conflicts:
libgmp3-dev.

I hope these were transient failures, as they happened after the hppa
buildds were recovered after a fairly long period of inactivity.

There are valid reasons to build-conflict on this package, so if the
FTBFS persists we'll have to think about a workaround.