gEDA: New autonumber text dialog

[Werner Hoch <werner_dot_ho-at-NOSPAMgmx_dot_de>]

Hi all,

I've commited the new source and some testschematics to CVS.
It has the following features:

* different selection levels (selection, current sheet, complete
  hierarchy)
* renumbering only unnumbered texts or all selected text elements
* select a starting number
* different sorting options (top down, left to right, diagonal)

Missing features:
* multipage (this can be achieved if you create a master file which
   contains the pages in its hierarchy)
* renumber all prefixes at once

Please test it and let me know whether you like it or if there are any 
bugs in it.

Special code organisation question: 
I put some constants at the beginning of the o_misc.nw file. Where shall 
I put them?
Is it better to use enums or definitions?

regards
Werner