How to make and apply patches
From Wikifications
Once you have the needed changes, apply them (pre autoconf) to a copy of a fresh source directory. You should now have a 'patched' directory sitting alongside an unpatched direcetory. Now generate the patch...
diff -ruN old new > my_patch
To apply this patch to a fresh source directory, place the patch alongside the source dir:
patch -p0 < my_patch