[Ecls-list] Critical change

[Juan Jose Garcia-Ripoll]

* Visible changes:

 - Function ecl_stream_to_handle() now exported.

 - Function backup_fopen() renamed to ecl_backup_fopen().

 - Minimized the number of headers included by ecl/ecl.h. In particular,
   stdio.h, inittypes.h and pthread.h are no longer used.

These changes are motivated by some future improvements in the UFFI /
CFFI layers and their goal is to minimize the number of C symbols
which are defined when including ecl/ecl.h

In doing so I have run through the list of included headers, comparing
them with the content of the open standards (www.opengroup.org, for
instance) and keeping only headers that define basic C types (size_t,
int8_t, etc).

Note that not all platforms follow the ISO and POSIX standards, so my
choice of headers might break some ports. I have tried to avoid it, by
keeping most of the #ifdef's from the previous version of the code.
But should you run intro problems with CVS, please report it
immediately to the mailing list.

Juanjo