Path to plugins overriding support & CVE's fixes
    
    - added patch that fixes stack-overflow vulnerability in lsx_ms_adpcm_block_expand_i (CVE-2017-15372)
      + resolves #1500553, #1510919
    - added patch that fixes use-after-free in lsx_aiffstartread (CVE-2017-15642)
      + resolves #1510923
    - added patch that fixes incorrect FSF address in src/ladspa.h
    - added patch that introduces SOX_PLUGINS environment variable that overrides
      standard sox location for plugins
    - added patch that inserts $(DESTDIR) before ${bindir} in src/Makefile.am
      installcheck target
    - added tests that checks if previously fixed bugs remain fixed in newer releases
    - spec file changes:
      + suppressed rpmlint warning about bad Source URL
      + added comments to security patches
      + in %description: added missing sentence period
      + in %prep: suppressed "%setup is not quite" rpmlint warning
      + in %install: removed redundant slashes before %{_libdir}
      + added %check section