* tests/defs (required): Handle `gcc' and `g++'; automatically export CC and CXX when they are required. * tests/ansi3.test, tests/ansi5.test, tests/ccnoco.test, tests/cond4.test, tests/cond16.test, tests/cond18.test, tests/cond19.test, tests/depcomp2.test, tests/depend2.test, tests/lex3.test, tests/pr87.test, tests/pr220.test, tests/substref.test, tests/target-cflags.test, tests/yacc4.test, tests/yaccvpath.test: Require gcc. Don't pass CC=gcc to configure. * tests/subobj9.test: Require g++.