* tests/atlocal.in (GCC): Add.

* tests/calc.at: s/m4_match/m4_bmatch/.
s/m4_patsubst/m4_bpatsubst/.
(AT_CHECK_CALC): Check the compiler's stderr only if it's GCC.
* configure.in: AC_SUBST(GCC).

configure.in

@@ -27,6 +27,8 @@ AM_CONFIG_HEADER(config.h:config.hin)
 # Initialize the test suite.
 AC_CONFIG_TESTDIR(tests)
 AC_CONFIG_FILES([tests/bison], [chmod +x tests/bison])
+# Needed by tests/atlocal.in.
+AC_SUBST([GCC])
 
 # Checks for programs.
 AC_PROG_CC