[Firebird-docs] Update documents

[Mark R. <ma...@la...>]

I have finally added links to the German Firebird 2.5 Language Reference 
I migrated last week, and also updated and linked the English 
documentation for isql, gsec, gbak, gstat, gfix, fbmgr, gsplit and shell 
scripts.

I think I will not migrate the Russian and Portuguese counterparts of 
these (only gsplit/gsec) as those seem to be older versions as they are 
still part of the Firebird Utilities book, instead of separate books. It 
is probably better to redo the translation from scratch. If there are 
other opinions about this, let me know; I can still migrate them if 
necessary.

Next I'll do the Firebird 3.0 Developer's Guide.

Mark
-- 
Mark Rotteveel