Fix compiler warnings in Sha1.c.

These warnings are false positives emitted by GCC; there are no errors
in the code. By changing the parameter type to a pointer, we prevent
GCC from making faulty assumptions about the code.

src/Sha/Sha1.c

@@ -60,7 +60,7 @@ typedef struct
 } Sha1Context;
 
 static void
-Sha1Transform(uint32_t state[5], const uint8_t buffer[64])
+Sha1Transform(uint32_t state[5], const uint8_t *buffer)
 {
     uint32_t a, b, c, d, e, i;
     uint8_t workspace[64];