Set up the compiler to ptrace the runtime

[water111]

Add a library xdbg which should hide the details of cross platform debugging.
Implement ptrace attach/detach for linux only in xdbg
Make the runtime send the compiler all the info needed to attach.
Make the Listener remember loads / reset messages for the debugger.
Some very basic logic to attach/detach, and a simple test.

Needs more documentation and a better way to manage debugger state before merging. Maybe we want a Debugger object to hold all this state?

[coveralls]

Pull Request Test Coverage Report for Build 339367452

• 343 of 443 (77.43%) changed or added relevant lines in 19 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.03%) to 81.909%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
game/kernel/ksocket.cpp	8	9	88.89%
test/goalc/framework/test_runner.cpp	1	2	50.0%
game/kernel/klisten.cpp	3	5	60.0%
game/kernel/kprint.cpp	9	12	75.0%
goalc/listener/Listener.cpp	70	74	94.59%
goalc/compiler/Compiler.cpp	24	31	77.42%
goalc/debugger/Debugger.cpp	54	62	87.1%
common/cross_os_debug/xdbg.cpp	74	107	69.16%
goalc/compiler/compilation/Debug.cpp	6	47	12.77%

Totals
Change from base Build 336934547:	-0.03%
Covered Lines:	15475
Relevant Lines:	18893

---

💛 - Coveralls

[water111]

This adds a very basic debugging framework. The C Kernel now sends some info to the compiler so the debugger can find the correct process. The compiler can now "attach" to a target with (dbg), and break/continue with (:break) and (:cont). We can also read/write memory by GOAL address and get x86 GPRs, but this isn't exposed at the compiler REPL yet, other than a (:dump-all-mem <file>) that dumps all GOAL memory to a file for later debugging.

Right now this only works in Linux, but the platform specific stuff is stubbed out in xdbg.cpp. The debugger tests only run in linux.