Tests: Add workaround to Wrapping test for Watcom failure

The Watcom tools do not seem to like our wrapFLTK executable
to mix C and C++ sources.  Work around this by using C++ for
both sources.

Tests/Wrapping/CMakeLists.txt

@@ -93,7 +93,7 @@ add_library(wraplibFLTK ${wraplibFLTK_FLTK_UI_SRCS})
 add_dependencies(wraplibFLTK fakefluid)
 add_dependencies(fakefluid Wrap)
 fltk_wrap_ui (wrapFLTK fltk2.fl)
-add_executable(wrapFLTK wrapFLTK.c ${wrapFLTK_FLTK_UI_SRCS})
+add_executable(wrapFLTK wrapFLTK.cxx ${wrapFLTK_FLTK_UI_SRCS})
 target_link_libraries(wrapFLTK wraplibFLTK)
 add_dependencies(wrapFLTK fakefluid)