mhd_norm_expd.m4: added autoconf helper macro

m4/mhd_norm_expd.m4

@@ -0,0 +1,21 @@
+# SYNOPSIS
+#
+#   _mhd_norm_expd([macro])
+#
+# DESCRIPTION
+#
+#   Normalize string after expansion of the macros.
+#
+#
+# LICENSE
+#
+#   Copyright (c) 2022 Karlson2k (Evgeny Grin) <k2k@narod.ru>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 1
+
+AC_DEFUN([_mhd_norm_expd],[m4_normalize(m4_expand([$1]))])