platforms.

So in a sense this commit reverts few latest ones fixing bugs in original
code and improving it, most notably adding 64-bit support [though not in
BN_nist_mod_224 yet].
PR: 1593

PR: 1593

will be revised too.
PR: 1593

PR: 1593

for now (it was broken anyway)

Remove certain redundant BN_zero() initialisations, because BN_CTX_get(),
BN_init(), [etc] already initialise to zero.

Correct error checking in bn_sqr.c, and be less wishy-wash about how/why
the result's 'top' value is set (note also, 'max' is always > 0 at this
point).

redefine bn_clear_top2max() to be a NOP in the non-debugging case, and
remove some unnecessary usages in bn_nist.c.

Submitted by: Nils Larsch
Reviewed by: Geoff Thorpe, Ulf Möller

automatically to accomodate the value, some compilers fail to do so. Most
notably 0x0123456789ABCDEF should come out as long long in 32-bit context,
but HP compiler truncates it to 32-bit value. Which in turn breaks GF(2^m)
arithmetics in hpux-parisc2-cc build. Therefore this fix...

constant BIGNUMs. It turns out that this trips up different but equally
useful compiler warnings to -Wcast-qual, and so wasn't worth the ugliness
it created. (Thanks to Ulf for the forehead-slap.)

is itself experimental, and in addition may cause execution to break on
existing openssl "bugs" that previously were harmless or at least
invisible.

and structures as constant without having to cast away const at any point.
There is still plenty of other code that makes gcc's "-Wcast-qual" unhappy,
but crypto/bn/ is now ok. Purists are welcome to suggest alternatives.

structures being passed in to or out of API functions, and this corrects a
couple of cases found so far.

Also, lop off a couple of bytes of white-space.

create new lock CRYPTO_LOCK_BN to avoid race condition

Submitted by: Nils Larsch