Fix 'cord' headers path in EMX_MAKEFILE and README.QUICK

* EMX_MAKEFILE (CORD_INCLUDE_FILES): Replace cord/*.h files with
include/*.h ones (all "cord" header files moved in gc4.8).
* EMX_MAKEFILE (cords): Do not copy cord/*.h files to "include"
folder.
* README.QUICK: Replace cord/cord.h with include/cord.h; move sentence
about cord.h to the relevant paragraph.