Merging files to one

[Tor Lillqvist]

The number of source code lines in a .cxx file is as such not that
relevant a factor determining resources consumed when compiling a
source file. After all, the number of source lines *included* from
headers during the compilation can easily be much more. The complexity
of the code (especially so-called template-based metaprogramming) can
be a much larger factor.

As such, personally I also dislike the split of source code into
numbered source files. It has been done a long time ago when computers
were much much less powerful. But the main thing that speaks against
re-combining source code files that clearly "belongs" together into
one source file is the loss of (easy) access to version history.

--tml