Skip tests that require USE=debug when building with USE=-debug

http://bugs.gentoo.org/286173

--- a/tests/Test-E-k-K.px
+++ b/tests/Test-E-k-K.px
@@ -3,6 +3,7 @@
 use strict;
 use warnings;
 
+use WgetFeature qw(debug);
 use HTTPTest;
 
 
--- a/tests/Test-cookies-401.px
+++ b/tests/Test-cookies-401.px
@@ -3,6 +3,7 @@
 use strict;
 use warnings;
 
+use WgetFeature qw(debug);
 use HTTPTest;
 
 
--- a/tests/Test-ftp-bad-list.px
+++ b/tests/Test-ftp-bad-list.px
@@ -3,6 +3,7 @@
 use strict;
 use warnings;
 
+use WgetFeature qw(debug);
 use FTPTest;
 
 
--- a/tests/Test-proxy-auth-basic.px
+++ b/tests/Test-proxy-auth-basic.px
@@ -3,6 +3,7 @@
 use strict;
 use warnings;
 
+use WgetFeature qw(debug);
 use HTTPTest;
 
 
--- a/tests/WgetFeature.cfg
+++ b/tests/WgetFeature.cfg
@@ -1,4 +1,5 @@
 %skip_messages = (
+    debug => "Not running test: Wget under test doesn't support debug.",
     https => "Not running test: Wget under test doesn't support HTTPS.",
     iri   => "Not running test: Wget under test doesn't support IDN/IRI.",
 );