core/crypto: Expose the block sizes for every hash algorithm

While I just went and made this private, this information is required
for keying HMAC.

core/crypto/legacy/md5/md5.odin

@@ -22,9 +22,12 @@ import "core:encoding/endian"
 import "core:math/bits"
 import "core:mem"
 
-// DIGEST_SIZE is the MD5 digest size.
+// DIGEST_SIZE is the MD5 digest size in bytes.
 DIGEST_SIZE :: 16
 
+// BLOCK_SIZE is the MD5 block size in bytes.
+BLOCK_SIZE :: 64
+
 // Context is a MD5 instance.
 Context :: struct {
 	data:    [BLOCK_SIZE]byte,
@@ -131,9 +134,6 @@ reset :: proc(ctx: ^$T) {
     MD5 implementation
 */
 
-@(private)
-BLOCK_SIZE :: 64
-
 /*
     @note(zh): F, G, H and I, as mentioned in the RFC, have been inlined into FF, GG, HH
     and II respectively, instead of declaring them separately.