Allow the \include qdoc command to include a snippet from a .qdocinc file instead of always including the entire file.

The \include qdoc command allows you to include a sequence of qdoc commands and text in the input stream to qdoc. This command is useful when you want to include a documentation snippet in multiple places in the documentation output. The command was limited in that it only allowed you to include an entire .qdocinc file in the input stream.

The command format has been altered to allow a second argument, e.g. \include <file-path> <snippet-name>, where <snippet-name> names a block of qdoc commands and text in the file identified by <file-path>. The block of qdoc commands and text is surrounded by:

//! [<snippet-name>]

...commands and text...

//! [<snippet-name>]