use inline 'libraryVersion()' function (closes #858)

include/internal/catch_version.h

@@ -32,7 +32,7 @@ namespace Catch {
         void operator=( Version const& );
     };
 
-    extern Version libraryVersion;
+    inline Version libraryVersion();
 }
 
 #endif // TWOBLUECUBES_CATCH_VERSION_H_INCLUDED

include/internal/catch_version.hpp

@@ -37,7 +37,10 @@ namespace Catch {
         return os;
     }
 
-    Version libraryVersion( 1, 8, 2, "", 0 );
+    inline Version libraryVersion() {
+        static Version version(1, 8, 2, "", 0);
+        return version;
+    }
 
 }