Fix some infrastructure to be able to cope with host and target

Fix some infrastructure to be able to cope with host and target
machines with different sized basic types (ints, ptrs, etc).
(Idea from pierre@la.tce.com (Pierre Willard).)

* values.c (value_from_longest):  Rename from value_from_long.
Handle pointer types as well as integers, so that targets with
different pointer sizes from the host can be accomodated.
* breakpoint.c, convex-tdep.c, eval.c, expprint.c, printcmd.c,
valarith.c, valops.c, valprint.c, value.h, values.c:  Rename
uses of value_from_long to value_from_longest.