Merge lp://staging/~pitti/notify-osd/link-gcc-4.5 into lp://staging/notify-osd/lucid

When building current trunk on natty, I get a lot of errors like

  CCLD notify-osd
/usr/bin/ld.bfd.real: notify_osd-bubble.o: undefined reference to symbol 'XDeleteProperty'
/usr/bin/ld.bfd.real: note: 'XDeleteProperty' is defined in DSO /usr/lib64/libX11.so.6 so try adding it to the linker command line
/usr/lib64/libX11.so.6: could not read symbols: Invalid operation

/usr/bin/ld.bfd.real: notify_osd-gaussian-blur.o: undefined reference to symbol 'pixman_image_composite'
/usr/bin/ld.bfd.real: note: 'pixman_image_composite' is defined in DSO /usr/lib64/libpixman-1.so.0 so try adding it to the linker command line
/usr/lib64/libpixman-1.so.0: could not read symbols: Invalid operation

  CCLD test-modules
/usr/bin/ld.bfd.real: test_modules-bubble.o: undefined reference to symbol 'XDeleteProperty'
/usr/bin/ld.bfd.real: note: 'XDeleteProperty' is defined in DSO /usr/lib64/libX11.so.6 so try adding it to the linker command line

gcc 4.5 with --as-needed has a stricter linking behaviour which requires explicit linking with all necessary libraries. Some programs use direct libX11 or libpixman functions, and thus need to link to them explicitly.