note Cache::FileCache uses sha1, so it's ok to use MD5
	(remember we're just using it on the key, not the value, so
	 we'll usually be giving it on the order of 100 bytes)

conclusion: just use MD5. it's fast enough and widely 
available/installed.

MD5:     1.405/1.397/1.396
newhash: 0.923/0.920/0.925

#MD5 is much faster than SHA1 (at least in perl)
#MD4 is marginally faster than MD5 (but less available)

#Pearson, JHash, Elf, DJB, FNV all show promise but don't outperform newhash 

#testing done on Athlon-XP downclocked to 1000MHz

#general notes:
#OO is faster
#using addfile instead of add is MUCH faster!

time perl -e 'use Digest::MD5 qw(md5 md5_hex md5_base64); for my $i 
(0..100) { open(FH, "foobar"); my $digest = md5(join ("", <FH>)); 
close(FH); } '
MD5:      4.806/4.731/4.752
MD4:      4.625/4.647/4.620
SHA1:     14.195/14.158/14.185
SHA2:     N/A
JHash:    4.266/4.277/4.333
Adler32:  N/A
Haval:    N/A
Elf:      3.519/3.500/3.443
Whirlpool:N/A
MD2:      (est. 55.14)
DJB:      3.500/3.523/3.509
Tiger:    6.941/6.887/6.940
Nilsimsa: segfault
Pearson:  4.375/4.435/4.405
FNV:      3.447/3.493/3.498

time perl -e 'use Digest::MD5 qw(md5 md5_hex md5_base64); for my $i 
(0..100) { open(FH, "foobar"); my $ctx = Digest::MD5->new; 
$ctx->add(<FH>); my $digest = $ctx->digest; close(FH); } '
MD5:      4.161/4.342/4.165
MD4:      4.081/4.039/4.050
SHA1:     13.656/13.545/13.585
SHA2:     7.770/7.741/7.734
JHash:    N/A
Adler32:  (est. 271.6)
Haval:    4.966/4.929/4.933
Elf:      N/A
Whirlpool:22.611/22.549/23.077
MD2:      (est. 54.55)
DJB:      N/A
Tiger:    N/A
Nilsimsa: N/A
Pearson:  N/A
FNV:      N/A

time perl -e 'use Digest::MD5 qw(md5 md5_hex md5_base64); for my $i 
(0..100) { open(FH, "foobar"); my $ctx = Digest::MD5->new; 
$ctx->addfile(FH); my $digest = $ctx->digest; close(FH); } '
MD5:      1.658/1.660/1.657
MD4:      1.561/1.591/1.602
SHA1:     11.115/11.164/11.199
SHA2:     error
JHash:    N/A
Adler32:  not tested (expected very slow)
Haval:    error
Elf:      N/A
Whirlpool:error
MD2:      (est. 52.03)
DJB:      N/A
Tiger:    N/A
Nilsimsa: N/A
Pearson:  N/A
FNV:      N/A