Avoid casting (void**) values.

Replaced with an expression that only casts (void*) values.

Author: roconnor-blockstream

src/util.h

@@ -141,7 +141,7 @@ static SECP256K1_INLINE void *manual_alloc(void** prealloc_ptr, size_t alloc_siz
     VERIFY_CHECK(((unsigned char*)*prealloc_ptr - (unsigned char*)base) % ALIGNMENT == 0);
     VERIFY_CHECK((unsigned char*)*prealloc_ptr - (unsigned char*)base + aligned_alloc_size <= max_size);
     ret = *prealloc_ptr;
-    *((unsigned char**)prealloc_ptr) += aligned_alloc_size;
+    *prealloc_ptr = (unsigned char*)*prealloc_ptr + aligned_alloc_size;
     return ret;
 }