> Stephan, why did you prohibit building mana.c without ROOT and HBOOK
> support? I think such a configuration is valid and should be allowed.

Oops, sorry, my fault. I forgto that people use mana.c without ROOT and 
HBOOK. The reason I made the change was that people forgot the -DHVAE_HBOOK 
in their makefile. In that case, no HBOOK init is done in mana.c and the 
first histogram booking in the user code crashes HBOOK.

So please take the #error statement out of mana.c (I'm away in two hours for 
one week), but think about preventing the above mentionend problem. I don't 
know any way for the makefile or mana.c to figure out if there is any HF1 
call in the user code. Actually HF1 should return a "proper" error message 
than just crashing.

One possibility is that we put an additional layer on top of the histogram 
boooking/filling. These macros are converted to their HBOOK or ROOT 
equivalents depending on the HAVE_HBOOK/HAVE_ROOT. If none of both is 
present, the histogram booking macro can produce a runtime error. This has 
the additional advantage that users can switch from HBOOK to ROOT without 
change of their user code.