GDB stub (#1583)

* gdbstub beginnings

* gdbstub: finish gdb impl things, next up is integration with melonDS

* holy fuck the gdbstub works

* gdb breakpoints work, but there's a mysterious crash on continue

* fix memory corruption that sometimes happened, and make resetting the console thru gdb work

* remove some gdb debug printing

* fix things in gdbstub

* separate option for enabling gdbstub

* add mode-dependent CPU registers

* C++ize the GDBstub code

* add gdbstub config in emu settings dialog

* make sure gdb is disabled when jit is enabled

* Remove unnecessary compiler flags, mark ARMJIT assembly code as no-execute-stack

This hardens the binary a little bit against common exploitation methods

* add option to wait for debugger attach on startup

* only insert GNU stack notes on linux

* disable gdbstub enable checkbox when jit is enabled

* fix non-linux incompatibilities

* enable gdbstub by default

* fix issues with gdbstub settings disable stuff

* format stuff

* update gdb test code

* Fix segfault when calling StubCallbacks->GetCPU()

C++ overrides are hard. Please I'm just a lowly C programmer.

* fix packet size not being sent correctly

Thanks to @GlowingUmbreon on Github for troubleshooting this

* fix select(2) calls (i should read docs more properly)

* fix GDB command sequencing/parsing issue (hopefully)

* [GDB] implement no-ack mode

* fix sending ack on handshake

* get lldb to work

src/frontend/qt_sdl/Config.cpp

@@ -146,6 +146,14 @@ bool DSiBatteryCharging;
 
 bool DSiFullBIOSBoot;
 
+#ifdef GDBSTUB_ENABLED
+bool GdbEnabled;
+int GdbPortARM7;
+int GdbPortARM9;
+bool GdbARM7BreakOnStartup;
+bool GdbARM9BreakOnStartup;
+#endif
+
 CameraConfig Camera[2];
 
 
@@ -337,6 +345,14 @@ ConfigEntry ConfigFile[] =
 
     {"DSiFullBIOSBoot", 1, &DSiFullBIOSBoot, false, true},
 
+#ifdef GDBSTUB_ENABLED
+    {"GdbEnabled", 1, &GdbEnabled, false, false},
+    {"GdbPortARM7", 0, &GdbPortARM7, 3334, true},
+    {"GdbPortARM9", 0, &GdbPortARM9, 3333, true},
+    {"GdbARM7BreakOnStartup", 1, &GdbARM7BreakOnStartup, false, true},
+    {"GdbARM9BreakOnStartup", 1, &GdbARM9BreakOnStartup, false, true},
+#endif
+
     // TODO!!
     // we need a more elegant way to deal with this
     {"Camera0_InputType", 0, &Camera[0].InputType, 0, false},