New tmpstore to store variables which are not required to be in the store.
Data in tmpstore is not shared between timesteps: it's really temporary
stuff, but is useful for sharing space amongst functions.

The store now CANNOT depend on stardata AT ALL. It is static data, which
is allocated just once at the beginning of runtime.

Changed most (all that are used, it seems) variables to local.
Moved "static" variables to store, tmpstore or common, depending
on whether they are data that should not change, data that is temporary
or data that depends on the contents of stardata, respectively.

Fixed memory leaks.

All ALLOC_CHECKS are now done in MALLOC, CALLOC and REALLOC.

Seems to -finally!- be truly thread safe.