Tidy up, including;
- Remove unused and unuseful debug cruft.
- Remove unnecessary 'top' fudging from BN_copy().
- Fix a potential memory leak and simplify the expansion logic in
  BN_bin2bn().

Submitted by: Nils Larsch
Reviewed by: Geoff Thorpe

crypto/bn/bn_lib.c

diff --git a/crypto/bn/bn_lib.c b/crypto/bn/bn_lib.c
index 789e9aa..bbefd80 100644
--- a/crypto/bn/bn_lib.c
+++ b/crypto/bn/bn_lib.c
@@ -526,10 +526,6 @@
 #endif
 
 	a->top=b->top;
-#ifndef BN_STRICT
-	if ((a->top == 0) && (a->d != NULL))
-		a->d[0]=0;
-#endif
 	a->neg=b->neg;
 	bn_check_top(a);
 	return(a);
@@ -643,8 +639,10 @@
 	unsigned int i,m;
 	unsigned int n;
 	BN_ULONG l;
+	BIGNUM  *bn = NULL;
 
-	if (ret == NULL) ret=BN_new();
+	if (ret == NULL)
+		ret = bn = BN_new();
 	if (ret == NULL) return(NULL);
 	bn_check_top(ret);
 	l=0;
@@ -654,13 +652,16 @@
 		ret->top=0;
 		return(ret);
 		}
-	if (bn_expand(ret,(int)(n+2)*8) == NULL)
-		return(NULL);
 	i=((n-1)/BN_BYTES)+1;
 	m=((n-1)%(BN_BYTES));
+	if (bn_wexpand(ret, (int)i) == NULL)
+		{
+		if (bn) BN_free(bn);
+		return NULL;
+		}
 	ret->top=i;
 	ret->neg=0;
-	while (n-- > 0)
+	while (n--)
 		{
 		l=(l<<8L)| *(s++);
 		if (m-- == 0)
@@ -684,7 +685,7 @@
 
 	bn_check_top(a);
 	n=i=BN_num_bytes(a);
-	while (i-- > 0)
+	while (i--)
 		{
 		l=a->d[i/BN_BYTES];
 		*(to++)=(unsigned char)(l>>(8*(i%BN_BYTES)))&0xff;