SCO_SV: Enable so filename versioning

Take changes used by pkgsrc [1]:

* so filename versioning requires CMAKE_SHARED_LIBRARY_SONAME_C_FLAG.

[1] http://cdn.netbsd.org/pub/pkgsrc/current/pkgsrc/devel/cmake/patches/

Modules/Platform/SCO_SV.cmake

@@ -1,2 +1,3 @@
 set(CMAKE_DL_LIBS "")
+set(CMAKE_SHARED_LIBRARY_SONAME_C_FLAG "-h,")
 include(Platform/UnixPaths)