Use ldconfig to find libraries

This fixes the dependency check when the libraries are not in /usr/lib. 64 bit openSUSE for instance uses /usr/lib64.
Use ldconfig for the libraries I had overlooked
Change all references to ldconfig to /sbin/ldconfig.
Change fix_vanilla_df_openal_issue() function to use ldconfig instead of find.
Revbump to 0.2.1.