Kernel: Add ptrace commands for reading/writing the debug registers

This adds PT_PEEKDEBUG and PT_POKEDEBUG to allow for reading/writing
the debug registers, and updates the Kernel's debug handler to read the
new information from the debug status register.

Kernel/UnixTypes.h

@@ -690,6 +690,8 @@ struct rtentry {
 #define PT_PEEK 7
 #define PT_POKE 8
 #define PT_SETREGS 9
+#define PT_POKEDEBUG 10
+#define PT_PEEKDEBUG 11
 
 // Used in struct dirent
 enum {