Follow changes in the testsuite

tests/fork/test.T

@@ -4,6 +4,6 @@ setTestOpts(compose(only_compiler_types(['ghc']),
 
 hpc_prefix = "perl ../hpcrun.pl --clear --exeext=" + config.exeext + " --hpc='" + config.hpc + "'";
 
-test('hpc_fork', [ if_os('mingw32', skip), # no forkProcess on Windows
+test('hpc_fork', [ when(opsys('mingw32'), skip), # no forkProcess on Windows
                    cmd_prefix(hpc_prefix) ], compile_and_run, ['-fhpc'])