Introduced a OSG_PLUGIN_PREFIX variable into CMake build system with it set to

"" for all platforms except Cygwin where its set to "cygwin_" and Mingw where
it is set to "mingw_".  Updated osgDB::Registry to look for these for the plugins.
Updated the osgintrospection example to search for these names as well.

src/osgDB/Registry.cpp

@@ -585,9 +585,9 @@ std::string Registry::createLibraryNameForExtension(const std::string& ext)
 #if defined(WIN32)
     // !! recheck evolving Cygwin DLL extension naming protocols !! NHV
     #ifdef __CYGWIN__
-        return prepend+"cyg"+"osgdb_"+lowercase_ext+".dll";
+        return prepend+"cygwin_"+"osgdb_"+lowercase_ext+".dll";
     #elif defined(__MINGW32__)
-        return prepend+"lib"+"osgdb_"+lowercase_ext+".dll";
+        return prepend+"mingw_"+"osgdb_"+lowercase_ext+".dll";
     #else
         #ifdef _DEBUG
             return prepend+"osgdb_"+lowercase_ext+"d.dll";

src/osgPlugins/CMakeLists.txt

@@ -11,15 +11,13 @@ IF(NOT MSVC)
     SET(LIBRARY_OUTPUT_PATH "${LIBRARY_OUTPUT_PATH}/${OSG_PLUGINS}")
 ENDIF(NOT MSVC)
 
-IF(NOT MINGW)
-    SET(CMAKE_SHARED_MODULE_PREFIX "")
-ENDIF(NOT MINGW)
+SET(CMAKE_SHARED_MODULE_PREFIX ${OSG_PLUGIN_PREFIX})
 
 
 SET(TARGET_DEFAULT_PREFIX "osgdb_")
 SET(TARGET_DEFAULT_LABEL_PREFIX "Plugins")
 SET(TARGET_COMMON_LIBRARIES 
-        OpenThreads
+    OpenThreads
     osg 
     osgDB 
     osgUtil

src/osgWrappers/CMakeLists.txt

@@ -2,9 +2,7 @@ PROJECT(OSG_WRAPPERS)
 
 SET(LIBRARY_OUTPUT_PATH "${LIBRARY_OUTPUT_PATH}/${OSG_PLUGINS}")
 
-IF(NOT MINGW)
-    SET(CMAKE_SHARED_MODULE_PREFIX "")
-ENDIF(NOT MINGW)
+SET(CMAKE_SHARED_MODULE_PREFIX ${OSG_PLUGIN_PREFIX})
 
 
 MACRO(ADD_WRAPPER_LIB SUBDIR EXPORTDEF)