Fix symbol visibility on gcc

qt/qextscintillaglobal.h

@@ -44,6 +44,12 @@
 #define	TQEXTSCINTILLA_EXPORT	__declspec(dllexport)
 #endif
 
+#else
+
+#if __GNUC__ >= 4
+#define TQEXTSCINTILLA_EXPORT __attribute__ ((visibility("default")))
+#endif
+
 #endif
 
 #if !defined(TQEXTSCINTILLA_EXPORT)