Add distprep target to take some of the job of the release_prep script.

The latter updated accordingly. Also add `dist' and `distcheck' targets
to play with, but caveat packager.

Updated backend/bootstrap and backend/parser makefile to make them
marginally builddir aware and fix the usual set of things.

Add rule to automatically remake config.h dependent on config.h.in and
config.status. (Adopted from Autoconf manual and about every other
package.) On a good day we should now have a complete and accurate set
of dependencies throughout everything.

configure

@@ -7850,11 +7850,12 @@ done
 ac_given_srcdir=$srcdir
 ac_given_INSTALL="$INSTALL"
 
-trap 'rm -fr `echo "GNUmakefile
-	src/GNUmakefile
-	src/Makefile.global
-	src/backend/port/Makefile
-	src/test/regress/GNUmakefile
+trap 'rm -fr `echo "
+  GNUmakefile
+  src/GNUmakefile
+  src/Makefile.global
+  src/backend/port/Makefile
+  src/test/regress/GNUmakefile
  src/include/config.h" | sed "s/:[^ ]*//g"` conftest*; exit 1' 1 2 15
 EOF
 cat >> $CONFIG_STATUS <<EOF
@@ -8011,10 +8012,10 @@ EOF
 cat >> $CONFIG_STATUS <<EOF
 
 CONFIG_FILES=\${CONFIG_FILES-"GNUmakefile
-	src/GNUmakefile
-	src/Makefile.global
-	src/backend/port/Makefile
-	src/test/regress/GNUmakefile
+  src/GNUmakefile
+  src/Makefile.global
+  src/backend/port/Makefile
+  src/test/regress/GNUmakefile
 "}
 EOF
 cat >> $CONFIG_STATUS <<\EOF
@@ -8231,6 +8232,7 @@ cat >> $CONFIG_STATUS <<EOF
 
 EOF
 cat >> $CONFIG_STATUS <<\EOF
+echo timestamp > src/include/stamp-h
 
 exit 0
 EOF