build-sys: Move to compiling with C11 support

This is needed for building with anonymous unions. A bunch of calls to
fail() that used to mysteriously work need fixing -- fail() is a macro
that takes a printf-style message as an argument. Not passing this
somehow worked with the previous compiler flags, but breaks with
-std=c11.

src/tests/get-binary-name-test.c

@@ -39,7 +39,7 @@ START_TEST (getbinaryname_test) {
         if (!pa_get_binary_name(exename, allocated)) {
             pa_log_error("failed to read binary name");
             pa_xfree(exename);
-            fail();
+            ck_abort();
         }
 
         if (strlen(exename) < allocated - 1) {