xdiskusage-1.51-bp151.3.1

- Only fltk-devel is needed for build since circa 2014
- install files manually, buildsystem wrongly strips binaries
  fixes debuginfo generation.
- force build scripts to honour CXXFLAGS

- Updated to new upstream version, 1.51.
- Removed xdiskusage-fltk13.patch and xdiskusage-remove-glu.patch as
  they are no longer needed due to the use of 'fltk-config' in
  the Makefile.

- Add xdiskusage-remove-glu.patch to remove unused GLU dependency
- Remove GLU dependency for !openSUSE distros

- built with fltk 1.3

- Update to version 1.48.1:
  + Utilises the release from the fork hosted on Google Code.