bootloader: Add a debugger() function.

Just like the kernel has.

Put in the same file with the user_memcpy wrapper,
and rename the file to "misc.cpp" (which is a name
also used in libroot_build for a file containing
miscellaneous wrapper functions.)

src/system/boot/loader/Jamfile

@@ -118,7 +118,7 @@ for platform in [ MultiBootSubDirSetup ] {
 			stdio.cpp
 			system_revision.c
 			vfs.cpp
-			vm.cpp
+			misc.cpp
 
 			# libroot
 			driver_settings.cpp

src/system/boot/loader/misc.cpp

@@ -15,3 +15,10 @@ user_memcpy(void* to, const void* from, size_t size)
 	memcpy(to, from, size);
 	return B_OK;
 }
+
+
+void
+debugger(const char *message)
+{
+	panic(message);
+}