Fix compiler warning in SHA1 implementation

Update the signature of sha1_final() to fix the following warning:

    sha1.c:208:43: warning: argument 2 of type ‘uint8_t[20]’ {aka
    ‘unsigned char[20]’} with mismatched bound [-Warray-parameter=]

Signed-off-by: Lukas Fleischer <lfleischer@calcurse.org>

src/sha1.h

@@ -52,6 +52,6 @@ typedef struct {
 
 void sha1_init(sha1_ctx_t *);
 void sha1_update(sha1_ctx_t *, const uint8_t *, unsigned int);
-void sha1_final(sha1_ctx_t *, uint8_t *);
+void sha1_final(sha1_ctx_t *, uint8_t[SHA1_DIGESTLEN]);
 void sha1_digest(const char *, char *);
 void sha1_stream(FILE *, char *);