No it is still there. Although it is handled a bit strange.
3D Texturing is still like an extension, so you have to initialize a function-pointer to that function first. However 3D texturing is not listed in the extension string, so you cannot find out, if it is supported, by looking at the extension string.
You have to try to get the function pointer and check if it is NULL, if so, 3D texturing is not supported.
You can initialize your stuff easily, by using an extension loading library like glew: http://glew.sourceforge.net/
3D texturing was promoted to a core feature in OpenGL 1.2. So check the GL version string first. If it is less than 1.2, then you should check the extension string.
Getting the function pointer is of course platform specific. On my machine it just works.
And the documentation is still in the spec and in the man pages.