obj folders fix

Partial backtrack of changes I made in !174 (merged). Apparently removing all the .gitignore files from /objs's subfolders removed the only reason Git was keeping the folders alive (Git doesn't care about empty folders as it turns out). So now they have .gitignores again, with a warning in each not to remove them.

objs/DC/SDL/Debug/.gitignore

+# DON'T REMOVE
+# This keeps the folder from disappearing