[cff] Fix Savannah bug #43661. * src/cff/cf2intrp.c (cf2_interpT2CharString) <cf2_cmdHSTEM, cf2_cmdVSTEM, cf2_cmdHINTMASK>: Don't append to stem arrays after hintmask is constructed. * src/cff/cf2hints.c (cf2_hintmap_build): Add defensive code to avoid reading past end of hintmask.