mods: add possibility of dumping modsets
pts-to: extract compatibleTypes

compatibleFunTypes is not still correct. We can still pass (char *) to
(void *) functions and similar. Let us extract the comparison to
compatibleTypes where we will handle all this.
pts-to: fix compatibleFunTypes for good

We can still pass (char *) to (void *) functions and similar. Fix it
by over-approximating and returning true if the params are pointers.
pts-to: fix regression in return call maps

The commit f775a9705e64b47ab6e77b14bc1174d559c0f017 (pts-to: handle
VarArg functions properly, take 2) introduced a regression to
CallMaps::collectReturnRuleCodes. We dereference there g, which is
only defined in the other branch. Fix it by checking for proper type.
slic: handle memset/memcpy correctly with field-sensitive pts-to

Both memcpy and memset DEFine all values from 0 to the size of
memset/memcpy (3rd argument). So take care of this.