Add 'libqxt/' from commit 'e537460e56'

git-subtree-dir: libqxt
git-subtree-mainline: 004eaa228c
git-subtree-split: e537460e56

libqxt/libqxt-gcc6.patch

@@ -0,0 +1,11 @@
+--- a/src/core/qxtslotjob.cpp	2011-11-24 16:10:32.000000000 -0600
++++ b/src/core/qxtslotjob.cpp	2016-03-07 16:20:32.758268253 -0600
+@@ -174,7 +174,7 @@ This uses QxtSignalWaiter so it will _no
+ 
+ QVariant QxtFuture::delayedResult(int msec)
+ {
+-    if (!waiter->wait(msec, false))
++    if (!waiter->wait(msec, NULL))
+         return QVariant();
+     return job->result();
+ }