autotools: revert '-std=gnu89' (commit f310326)

Apparently commit e2e868d fixed the remaining issues with gcc 5.x.
See also #1093, e2e868d,
and f310326.

src/configure

@@ -6900,55 +6900,6 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
 fi
-      if test 1 -gt 0; then :
-  { $as_echo "$as_me:${as_lineno-$LINENO}: checking if $CC supports -std=gnu89" >&5
-$as_echo_n "checking if $CC supports -std=gnu89... " >&6; }
-fi
-  ac_ext=c
-ac_cpp='$CPP $CPPFLAGS'
-ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
-ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
-ac_compiler_gnu=$ac_cv_c_compiler_gnu
-
-  ac_saved_cflags="$CFLAGS"
-  CFLAGS="-Werror -std=gnu89"
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-
-int
-main ()
-{
-
-  ;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
-  if test "1" -gt 0; then :
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
-$as_echo "yes" >&6; }
-fi
-      CFLAGS_EX="$CFLAGS_EX -std=gnu89"
-
-else
-  if test 1 -gt 0; then :
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-fi
-    if test "1" = 2; then :
-  as_fn_error $? "Not supported by compiler" "$LINENO" 5
-fi
-
-fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
-  CFLAGS="$ac_saved_cflags"
-  ac_ext=c
-ac_cpp='$CPP $CPPFLAGS'
-ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
-ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
-ac_compiler_gnu=$ac_cv_c_compiler_gnu
-
-
       if test 1 -gt 0; then :
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking if $CC supports -Wdate-time" >&5
 $as_echo_n "checking if $CC supports -Wdate-time... " >&6; }

src/configure.ac

@@ -269,8 +269,6 @@ fi
    JTR_FLAG_CHECK([-Wunused-but-set-variable], 1)
    dnl JTR_NOWARN_CHECK([unneeded-internal-declaration], 1)
    AS_IF([test "x$JTR_FLAG_Q_CHECK_WORKS" = xyes], [JTR_FLAG_CHECK([-Qunused-arguments],1)])
-   dnl Justified and Ancient (see issue 1093)
-   JTR_FLAG_CHECK([-std=gnu89], 1)
    dnl We like reproducible builds
    JTR_FLAG_CHECK([-Wdate-time], 1)
    JTR_LIST_ADD(CFLAGS_EXTRA, ["$CFLAGS_EX"])