Adds field to breakpoint struct to track how a breakpoint was
originally set, moves the logic for disabling and enabling a breakpoint
to proc.
This will allow creating suspended breakpoints that are automatically
enabled when a plugin is loaded. When follow exec mode is implemented
it will also be possible to automatically enable breakpoints (whether
or not they were suspended) on new child processes, as they are
spawned.

It also improves breakpoint restore after a restart, before this after
a restart breakpoints would be re-enabled using their file:line
position, for breakpoints set using a function name or a location
expression this could be the wrong location after a recompile.

Updates #1653
Updates #2551