ug.doc: Remove reference to old license
CompareIDs: change return type to int

This should fix a build failure on ppc64el:

+---
| wop.c: In function 'UG::INT OrderFathersXSH(UG::D3::MULTIGRID*, UG::D3::ELEMENT**)':
| wop.c:16705:60: error: invalid conversion from 'UG::INT (*)(const void*, const void*) {aka long int (*)(const void*, const void*)}' to '__compar_fn_t {aka int (*)(const void*, const void*)}' [-fpermissive]
|   qsort((void *)OE_Map, OE_nBndElem, sizeof(MAP), CompareIDs);
+---

Reference: https://launchpadlibrarian.net/174208169/buildlog_ubuntu-utopic-ppc64el.ug_3.10.0-1_FAILEDTOBUILD.txt.gz