Clean up bn_mont.c.

this is what we now use to read $RANDFILE / $HOME/.rnd.
(Previously, after 'cat'ting lots of stuff into .rnd
only the first MB would be looked at.)

Bugfix for apps/enc.c: Continue if RAND_pseudo_bytes returns 0
(only -1 is an error).

Workaround so that "make test" continues anyway.

Tidy up CRYPTO_EX_DATA structures.

opening the output file with "wb" to truncate it except on VMS
(where the file now keeps its original length because it is opened
with "rb+" -- does VMS have ftruncate?)

Slightly clarify the RAND_... documentation.

(we're now using fopen(..., "rb+") instead of fopen(..., "wb"),
so the file is not truncated automatically).

benefit of MS-DOS users.

non-function pointers to function pointers and vice versa.
The current solution is to have unions that describe the
conversion we want to do, and gives us the ability to extract
the type of data we want.

The current solution is a quick fix, and can probably be made
in a more general or elegant way.

((void *)0), by have a 0 instead.

which does no harm fixes that problem.

that are directly in crypto/, and prepare for a possible disabling of
certain messages that DEC C spews out.

are not guaranteed to be unpredictable.

(and rename a target in test/Makefile.ssl to make it
easier to guess the name of the file executed by it)

"key" is NULL.