Use TAP_TESTS_PERL to register the legacy_test in bin/pax.

Redo r260586 by using the new functionality in tap.test.mk to transparently
support perl-based test programs.

As a side-effect, we get rid of an explicit path to /usr/bin/perl by
replacing it with /usr/local/bin/perl (or as defined in tap.test.mk).

This also fixes the name of the legacy_test source file because this should
have always been legacy_test.pl and not legacy_test.sh.  My mistake when
originally moving the code around without realizing that this was a perl
script.

MFC after:	5 days

bin/pax/tests/Kyuafile

@@ -1,7 +0,0 @@
--- $FreeBSD$
-
-syntax(2)
-
-test_suite("FreeBSD")
-
-tap_test_program{name="legacy_test", required_programs="/usr/bin/perl"}

bin/pax/tests/Makefile

@@ -3,8 +3,7 @@
 .include <bsd.own.mk>
 
 TESTSDIR=	${TESTSBASE}/bin/pax
-KYUAFILE=	yes
 
-TAP_TESTS_SH=	legacy_test
+TAP_TESTS_PERL=	legacy_test
 
 .include <tap.test.mk>

bin/pax/tests/legacy_test.pl

@@ -1,5 +1,3 @@
-#! /usr/bin/perl
-#
 # $FreeBSD$
 
 use strict;