Quote/regex/wildcard audit (fixes issue #192)

Fix for issue #192

Added quotes around greps/cats to help alleviate possible problems with spaces in directory/file-names. Still the possibility for problems with ```include``` lines as they don't respect quotes, so would need escaping.

Removed ```$TARGETS``` as it was an unsafe wildcard and was only used in ```make clean``` which itself has been simplified to just delete the ```$OBJDIR``` rather than waste time deleting individual files.