Sort and remove duplicate entries in ALL_LIBS

Sort and remove duplicate entries in ALL_LIBS

- So far, configure showed e.g. the following at the end:
Libraries: -lgobject-2.0 -lpng -lm  -ldbi -lglib-2.0  -lpangocairo-1.0
 -lpango-1.0 -lgobject-2.0 -lglib-2.0 -lharfbuzz -lcairo  -lxml2

The variable ALL_LIBS included duplicates resulting from the configure
process and some double spaces.

- Now, ALL_LIBS is sorted and duplicate entries are removed, e.g.:
Libraries: -lcairo -ldbi -lglib-2.0 -lgobject-2.0 -lharfbuzz -lm
 -lpango-1.0 -lpangocairo-1.0 -lpng -lxml2