dependencies: temporarily use debugbreak fork

The following contribution fixes a gcc compilation issue on macOS:
scottt/debugbreak#25

This commit replaces the upstream repo with a fork until the above PR gets
integrated into the upstream master.

Author: MrAnno

.gitmodules

@@ -3,4 +3,4 @@
 	url = https://github.com/attractivechaos/klib.git
 [submodule "dependencies/debugbreak"]
 	path = dependencies/debugbreak
-	url = https://github.com/scottt/debugbreak
+	url = https://github.com/MrAnno/debugbreak.git