Increase the thread stack size to the default size on Linux, fixes
a crash.

Index: src/sshmasterconnection.cpp
--- src/sshmasterconnection.cpp.orig
+++ src/sshmasterconnection.cpp
@@ -152,7 +152,7 @@ SshMasterConnection::SshMasterConnection (QObject* par
         QString proxylogin, QString proxypassword, QString proxykey,
         bool proxyautologin, bool proxyKrbLogin ) : QThread ( parent )
 {
-#if defined ( Q_OS_DARWIN )
+#if defined ( Q_OS_DARWIN ) || defined(__OpenBSD__)
     // Mac OS X provides only 512KB stack space for secondary threads.
     // As we put a 512KB buffer on the stack later on, we need a bigger stack space.
     setStackSize (sizeof (char) * 1024 * 1024 * 2);