8175795: configure should verify that system zlib contains needed functionality Reviewed-by: erikj

8192854: FONTCONFIG_CFLAGS missing from spec.gmk.in Reviewed-by: erikj, prr

8189749: Devise strategy for making source level checks more uniform Summary: Create a 'feature' enum which is responsible for handling source version checks and related diagnostic generation Reviewed-by: jjg, jlahoda