$SHELL for $ac_install_sh?

[Karl Berry]

When a configure script has to fall back on $ac_install_sh for INSTALL
or MKDIR_P, how about invoking it via $SHELL, as in the diff below?

That way, if install-sh happens not to be executable, it will still work
-- it's called with $SHELL in other places.

Vincent Lefevre (cc'd, with thanks) reported this to me for Texinfo -- I
had neglected to make install-sh executable there, and he did not have
mkdir from coreutils.

Thanks,
Karl

--- /usr/local/gnu/src/autoconf-2.61/lib/autoconf/ORIG/programs.m4      
2006-08-25 13:48:02.000000000 -0700
+++ /usr/local/gnu/src/autoconf-2.61/lib/autoconf/programs.m4   2007-09-17 
17:51:39.000000000 -0700
@@ -587,3 +587,3 @@
     # removed, or if the value is a relative name.
-    INSTALL=$ac_install_sh
+    INSTALL="$SHELL $ac_install_sh"
   fi
@@ -681,3 +681,3 @@
     test -d ./--version && rmdir ./--version
-    MKDIR_P="$ac_install_sh -d"
+    MKDIR_P="$SHELL $ac_install_sh -d"
   fi