do not test colpack when user says no even when it is installed

--- configure.ac.orig	2012-07-19 13:04:37.426461811 -0700
+++ configure.ac	2012-07-19 13:06:06.477916144 -0700
@@ -281,7 +281,7 @@
 COLPACK_LIBDIR=""
 COLPACK_LIBS="-lColPack"
 ])
-
+if test x$colpack != xno; then
 AC_LANG_PUSH([C++])
 save_CPPFLAGS="$CPPFLAGS"
 save_LIBS="$LIBS"
@@ -301,7 +301,9 @@
 CPPFLAGS="$save_CPPFLAGS"
 LIBS="$save_LIBS"
 AC_LANG_POP([C++])
-
+else
+    have_colpack=no
+fi
 AM_CONDITIONAL(HAVE_LIBCOLPACK,[test x$have_colpack = xyes])
 if test x$have_colpack = xyes; then 
    sparse=yes