7.8 alpha 2

I've got some worries still on the Mac side:

- On PPC32 I've got strange core dumps from inside the JPEG library, but only if the _Image_JPEG module loads very late. I'm investigating a theory about conflicting symbols in the flat namespace. (Grubba and Agehall mentioned that Per might have seen this earlier. Any hints would be welcome.)

- On OS X 10.5 (at least for x86_64) I cannot build GMP into a relocatable library since Apple dropped a necesary ld flag that existed in 10.4 and earlier. That in turn means I need to disable dynamic modules. I'd like to improve this by converting Pike's GMP module to static linking while having the remaining modules dynamic since Pike always loads GMP anyway for bignum support.