Add catv (separate applet instead of cat -v). Also cleanup cat.c comments,

Add catv (separate applet instead of cat -v).  Also cleanup cat.c comments,
the following of which (from cat.c) belongs in svn history instead of the
source code:

/* Mar 16, 2003      Manuel Novoa III   (mjn3@codepoet.org)
 *
 * This is a new implementation of 'cat' which aims to be SUSv3 compliant.
 *
 * Changes from the previous implementation include:
 * 1) Multiple '-' args are accepted as required by SUSv3.  The previous
 *    implementation would close stdin and segfault on a subsequent '-'.
 * 2) The '-u' options is required by SUSv3.  Note that the specified
 *    behavior for '-u' is done by default, so all we need do is accept
 *    the option.
 */