Allow make to uninstall ecl

Currently make uninstall doesn't correctly uninstall ecl. Not only is this 'unclean' but it can cause problems for subsequent installs.

There are two reasons for this: 1) some paths have a double forward slash, i.e. /usre/local/lib//ecl. While this works when copying files to the install location. rm rejects such paths, 2) not all the paths specified in the install section are included in the remove section. This patch attempts to resolve both issues.

It should be noted that the mechanism used to remove the installation (both in the original and in my revision) is dangerous since it uses an rm -rf with paths built using make variables which are notoriously tricky to debug correctly. Perhaps a tool like cmake could make this more reliable?

Let me know if there is a better way to submit patches for consideration and thanks for all the great work!