Update source file names in comments and docs.

Correcting a source file name in the docs just now reminded me that
I've seen a lot of outdated source file names elsewhere in the code,
due to all the reorganisation since we moved to cmake. Here's a giant
pass of trying to make them all accurate again.

crypto/blowfish.h

@@ -1,5 +1,5 @@
 /*
- * Header file shared between sshblowf.c and sshbcrypt.c. Exposes the
+ * Header file shared between blowfish.c and bcrypt.c. Exposes the
  * internal Blowfish routines needed by bcrypt.
  */
 

crypto/ecc-ssh.c

@@ -548,8 +548,8 @@ static EdwardsPoint *eddsa_decode(ptrlen encoded, const struct ec_curve *curve)
     mp_free(y);
 
     /* A point constructed in this way will always satisfy the curve
-     * equation, unless ecc.c wasn't able to construct one at all, in
-     * which case P is now NULL. Either way, return it. */
+     * equation, unless ecc-arithmetic.c wasn't able to construct one
+     * at all, in which case P is now NULL. Either way, return it. */
     return P;
 }
 

crypto/mpint_i.h

@@ -266,7 +266,7 @@
 #endif /* DEFINE_BIGNUMDBLINT */
 
 /* ----------------------------------------------------------------------
- * Data structures used inside bignum.c.
+ * Data structures used inside mpint.c.
  */
 
 struct mp_int {