0026852: Coding - compiler warnings issued by GCC 5.2.1

Compiler warnings eliminated:
- BRepAlgo_DSAccess: avoid copying of local list
- IntPatch, IntTools: initialize "possibly used uninitialized" variables by zeros
- Intf: slight refactoring
- OSD_signal: suppress unused argument
- OpenGL: add missing initializers in structures
- STEPConstruct_GDTProperty: correct function signature to pass output parameters by reference

src/OSD/OSD_signal.cxx

@@ -343,7 +343,8 @@ static void SegvHandler(const int theSignal,
     return;
   }
 #else
-  (void )theContext;
+  (void)theSignal; // silence GCC warnings
+  (void)theContext;
 #endif
 #ifdef linux
   if (fFltExceptions)