configure: move definitions of private m4 macros before AC_INIT invocation

This way, no spurious comments nor whitespace will be propagated in the
generated configure script.

This change is a pure code movement (plus addition of a comment line).
Signed-off-by: NStefano Lattarini <stefano.lattarini@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

configure.ac

 #                                               -*- Autoconf -*-
 # Process this file with autoconf to produce a configure script.
 
-AC_PREREQ(2.59)
-AC_INIT([git], [@@GIT_VERSION@@], [git@vger.kernel.org])
-
-AC_CONFIG_SRCDIR([git.c])
-
-config_file=config.mak.autogen
-config_append=config.mak.append
-config_in=config.mak.in
-
-echo "# ${config_append}.  Generated by configure." > "${config_append}"
-
-
 ## Definitions of macros
 # GIT_CONF_APPEND_LINE(LINE)
 # --------------------------
@@ -137,6 +125,19 @@ if test -n "$1"; then
 fi
 ])
 
+## Configure body starts here.
+
+AC_PREREQ(2.59)
+AC_INIT([git], [@@GIT_VERSION@@], [git@vger.kernel.org])
+
+AC_CONFIG_SRCDIR([git.c])
+
+config_file=config.mak.autogen
+config_append=config.mak.append
+config_in=config.mak.in
+
+echo "# ${config_append}.  Generated by configure." > "${config_append}"
+
 # Directories holding "saner" versions of common or POSIX binaries.
 AC_ARG_WITH([sane-tool-path],
   [AS_HELP_STRING(