Debugger: va_list 'args' opened but not closed by va_end()

pointed out by cppcheck

Change-Id: Idf81666674c881ca9e00bf3985ed0dcf928c19d5
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4220
Reviewed-by: Jérôme Duval <jerome.duval@gmail.com>
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>

Debugger: Split into core library and application.

- Add subfolder src/kits/debugger which contains the debugger's core
functionality and lower layers. Correspondingly add headers/private/debugger
for shared headers to be used by clients such as the Debugger application
and eventual remote_debug_server. Adjust various files to account for
differences as a result of the split and moves.
- Add libdebugger.so to minimal Jamfile.