t1450: use egrep for regexp "alternation"

GNU grep allows "\(A\|B\)" as alternation in BRE, but this is an
extension not understood by some other implementations of grep
(Michael Kebe reported an breakage on Solaris).

Rewrite the offending test to ERE and use egrep instead.

Noticed-by: Michael Kebe <michael.kebe@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1450-fsck.sh

@@ -541,7 +541,7 @@ test_expect_success 'fsck --name-objects' '
 		remove_loose_object $(git rev-parse julius:caesar.t) &&
 		test_must_fail git fsck --name-objects >out &&
 		tree=$(git rev-parse --verify julius:) &&
-		grep "$tree (\(refs/heads/master\|HEAD\)@{[0-9]*}:" out
+		egrep "$tree \((refs/heads/master|HEAD)@\{[0-9]*\}:" out
 	)
 '