From Bob Kuehne, added osg::getGlVersion() and fixed a minor typo in Texture3D.

src/osg/GLExtensions.cpp

@@ -28,6 +28,14 @@
 #include <windows.h>
 #endif
 
+float osg::getGLVersionNumber()
+{
+    // needs to be extended to do proper things with subversions like 1.5.1, etc.
+    char *versionstring   = (char*) glGetString( GL_VERSION );
+    std::string vs( versionstring );
+    return( atof( vs.substr( 0, vs.find( " " ) ).c_str() ) );
+}
+
 bool osg::isGLExtensionSupported(unsigned int contextID, const char *extension)
 {
     typedef std::set<std::string>  ExtensionSet;