autogen.sh: update/copy over from mesa

This commit addresses three concerns:
 - Places quotes around variables. Otherwise things will fail badly if
either one of then contains space.
 - Adds --force to autoreconf, which will ensure that the build is
regenerated, if one updates autotools.
 - Honours the NOCONFIGURE variable, which is set by gnome-continuous
(iirc).
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Aaron Plattner <aplattner@nvidia.com>

autogen.sh

 #! /bin/sh
 
-srcdir=`dirname $0`
+srcdir=`dirname "$0"`
 test -z "$srcdir" && srcdir=.
 
 ORIGDIR=`pwd`
-cd $srcdir
+cd "$srcdir"
 
-autoreconf -v --install || exit 1
-cd $ORIGDIR || exit $?
+autoreconf --force --verbose --install || exit 1
+cd "$ORIGDIR" || exit $?
 
-$srcdir/configure "$@"
+if test -z "$NOCONFIGURE"; then
+    "$srcdir"/configure "$@"
+fi