Fix use of `require` in mysql-test-run.

The motivation for this is that Perl is moving towards not having
current directory ./ in @INC by default. This is causing
mysql-test-run.pl to fail in latest Debian Unstable:

  https://lists.debian.org/debian-devel-announce/2016/08/msg00013.html

However, we have `use "lib"`, there is no need for current directory
in @INC, except for a gross hack. In mtr_cases.pm, there is a
`require "mtr_misc.pl"`, which hides mtr_misc.pl away in mtr_cases
namespace. And things only work because mysql-test-run.pl loads it
with a different name, `require "lib/mtr_misc.pl"`! (Perl will
`require` only once for each unique filename).

Fix this by only using `require` in main program, and referencing
functions with :: scope from other namespaces. For multi-use in
different namespaces, proper `use` modules should be used.
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>

mysql-test/lib/mtr_cases.pm

@@ -60,8 +60,6 @@ use My::Test;
 use My::Find;
 use My::Suite;
 
-require "mtr_misc.pl";
-
 # locate plugin suites, depending on whether it's a build tree or installed
 my @plugin_suitedirs;
 my $plugin_suitedir_regex;
@@ -1098,7 +1096,7 @@ sub get_tags_from_file($$) {
   $file_to_tags{$file}= $tags;
   $file_to_master_opts{$file}= $master_opts;
   $file_to_slave_opts{$file}= $slave_opts;
-  $file_combinations{$file}= [ uniq(@combinations) ];
+  $file_combinations{$file}= [ ::uniq(@combinations) ];
   $file_in_overlay{$file} = 1 if $in_overlay;
   return @{$tags};
 }

mysql-test/lib/mtr_report.pm

@@ -34,7 +34,6 @@ use mtr_match;
 use My::Platform;
 use POSIX qw[ _exit ];
 use IO::Handle qw[ flush ];
-require "mtr_io.pl";
 use mtr_results;
 
 my $tot_real_time= 0;
@@ -92,7 +91,7 @@ sub mtr_report_test_passed ($) {
   my $timer_str=  "";
   if ( $timer and -f "$::opt_vardir/log/timer" )
   {
-    $timer_str= mtr_fromfile("$::opt_vardir/log/timer");
+    $timer_str= ::mtr_fromfile("$::opt_vardir/log/timer");
     $tinfo->{timer}= $timer_str;
     resfile_test_info('duration', $timer_str) if $::opt_resfile;
   }

mysql-test/mysql-test-run.pl

@@ -102,11 +102,11 @@ use mtr_results;
 use IO::Socket::INET;
 use IO::Select;
 
-require "lib/mtr_process.pl";
-require "lib/mtr_io.pl";
-require "lib/mtr_gcov.pl";
-require "lib/mtr_gprof.pl";
-require "lib/mtr_misc.pl";
+require "mtr_process.pl";
+require "mtr_io.pl";
+require "mtr_gcov.pl";
+require "mtr_gprof.pl";
+require "mtr_misc.pl";
 
 $SIG{INT}= sub { mtr_error("Got ^C signal"); };
 $SIG{HUP}= sub { mtr_error("Hangup detected on controlling terminal"); };