When stack watchpoints go out of scope simultaneously they can hide (or
duplicate the effect) of other breakpoints (including other watchpoints
going out of scope) that are placed on the same physical memory
location.
This happens because we delete the watchpoint-out-of-scope breakpoint
while we are evaluating hit breakpoints, mangling the breaklets list.
This commit moves breakpoint deletion out of the
watchpoint-out-of-scope condition, delaying it until all hit
breakpoints have been evaluated.
Also fix bug where on amd64 if all four watchpoints are in use the last
one is not checked.
Fixes#3739
Adds the low-level support for watchpoints (aka data breakpoints) to
the native linux/amd64 backend.
Does not add user interface or functioning support for watchpoints
on stack variables.
Updates #279
