Merge bitcoin-core#458: Fix typo in API documentation

b0452e6 Fix typo in API documentation (Tim Ruffing)

Pull request description:

Tree-SHA512: 0376756fc36004e9bb205c6b811e8b28ecd595db1fc2b577bf27c5c227d81ec8bca2e44cfab91fb76c9640d0f7c99970ce9ab94d72e26289cc8faeb747337309

Author: sipa

include/secp256k1.h

@@ -61,7 +61,7 @@ typedef struct {
  *  however guaranteed to be 64 bytes in size, and can be safely copied/moved.
  *  If you need to convert to a format suitable for storage, transmission, or
  *  comparison, use the secp256k1_ecdsa_signature_serialize_* and
- *  secp256k1_ecdsa_signature_serialize_* functions.
+ *  secp256k1_ecdsa_signature_parse_* functions.
  */
 typedef struct {
     unsigned char data[64];