Add test case for update hooks in receive-pack.

Add test case for update hooks in receive-pack.

Verify that the update hooks work as documented/advertised.  This is
a simple set of tests to check that the update hooks run with the
parameters expected, have their STDOUT and STDERR redirected to
the client side of the connection, and that their STDIN does not
contain any data (as its actually /dev/null).

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>