Hello,

This patch modifies dump.exp's capture_value function so that it:

- slurps output up to "(gdb)"
Stop GDB and dejagnu getting out-of-sync

- allow `invalid memory access' as a `value'
Stop double fail from an invalid value also not matching the old value.

Both of these are to stop dump.exp loosing the plot when gdb is broken.

Tested on mips-sim (it no longer hangs for several hours :-^); and 
NetBSD/PPC, it passes.

m'kay?
Andrew