meson: Create duplicate cursors via symlinks at install time

In !49 (merged) (Commit 7a5dc9d5), the duplicate cursors (aliases for cursor names) were switched from being symlinks to being copies to avoid problems with using symlinks with meson's install_subdir function. However, copying the cursors needlessly inflates the size of the distribution tarball and distribution packages.

The cursors are only installed on unix-like systems, so the symlinks themselves are not a problem.

To solve this problem, I have deleted the duplicate cursor files, and set up meson to create the required symlinks at install time. The list of symlinks to create is derived from the list of copied symlinks from the make.sh file (it has been updated to no longer create the copies).