Added t/head.pl as a simple version of head(1) for use during testing

1) Added t/head.pl as a simple version of head(1) for use during testing
   (pmall takes a long time to list all modules -- t/head.pl lets us
   take a shortcut by looking at only a few lines of pmall's output).
Fixed tests to use Tie::Hash (pure Perl) instead of Scalar::Util

1) Fixed tests to use Tie::Hash (pure Perl) instead of Scalar::Util.
   Scalar::Util exists both as pure Perl and Perl + XS, which means
   there may not be a Scalar/Util.pm to find depending on how Perl
   was packaged and installed.
2) Fixed t/pmall.t to use t/head.pl to head(1) the pmall output,
   then I matches only against the general form of pmall output
   rather than specifically looking for Scalar::Util (see (1) above).
Fixed t/pman.t and t/pmdesc.t to use the Carp module as Tie::Hash may be PODless

1) Fixed t/pman.t and t/pmdesc.t to use the Carp module as Tie::Hash may be
   PODless depending on the Perl version.
2) Fixed t/pmcheck.t to just check that pmcheck ran at all and had some
   output.
Fixed t/pmcat.t to use the module Carp because Tie::Hash may be PODless
Fixed t/pman.t to look for /[Cc]carp/ (capitalization changed in POD)
Fixed t/pmfunc.t to check for != 127 for a running pmfunc
Updated Changes for v1.51