Make exception_catchpoint inherit base_breakpoint instead of catchpoint

exception_catchpoint is really a code breakpoint, with locations set
by sals, re-set like other code breakpoints, etc., so make it inherit
base_breakpoint.

This adds a bit of duplicated code to exception_catchpoint's ctor
(copied from struct catchpoint's ctor), but it will be eliminated in a
following patch.

Change-Id: I9fbb2927491120e9744a4f5e5cb5e6870ca07009
1 file changed