Adjust documentation build for current doxygen versions

admin: Make build.sh do a parallel build and use 'nice'
admin: Make build.sh import an optional DOXYGEN envvar
senfscons: Allow setting arbitrary simple build environment variables from the command line

Examples: Autogenerate Mainpage.dox
HowTos/NewPacket: Start new howto

Fix TAGFILE dependencies
Fix some URL references
PPI: Add additional 'route' documentation
Globally disable SUBGROUPING in Doxygile.global

autogenerate list of search indices
replace @TOPDIR@ in html templates with relative path to project root

Unified emacs Local Variables

Add HTML tidy postprocessing and error filtering to SENFScons doxygen method
Add doclib/filter.pl INPUT_FILTER to fix example code indentation in the documentation
Add a glossary to the Socket documentation
Furthher Socket library docs (Protocol classes)

Extend the CSS rules some more for advanced browsers (probably everyone except IE)

Finish FileHandle documentation
Complete SocketHandle documentation

Updated documentation templates to include cross-reference
Fixed documentation build (especially regarding cleanup)
Cleaned up BUG, FIXME, TODO and IDEA items
More SocketLibrary documentation

Add MAXWIDTH support to Dia2Png builder
Start Socket library documentation

Add optional local configfile 'Doxyfile.local'

Renaned directory satscons to senfscons

Add additional templates