Remove implicit pointer types conversions.

See also: https://wiki.gentoo.org/wiki/Modern_C_porting
Bug: https://bugs.gentoo.org/919066
Upstream PR: https://github.com/gdraheim/zziplib/pull/150

--- a/SDL/SDL_rwops_zzip.c
+++ b/SDL/SDL_rwops_zzip.c
@@ -15,17 +15,17 @@
 #define SDL_RWOPS_ZZIP_FILE(_context)  (ZZIP_FILE*) \
              ((_context)->hidden.unknown.data1)
 
-static int _zzip_seek(SDL_RWops *context, int offset, int whence)
+static Sint64 _zzip_seek(SDL_RWops *context, Sint64 offset, int whence)
 {
     return zzip_seek(SDL_RWOPS_ZZIP_FILE(context), offset, whence);
 }
 
-static int _zzip_read(SDL_RWops *context, void *ptr, int size, int maxnum)
+static size_t _zzip_read(SDL_RWops *context, void *ptr, size_t size, size_t maxnum)
 {
     return zzip_read(SDL_RWOPS_ZZIP_FILE(context), ptr, size*maxnum) / size;
 }
 
-static int _zzip_write(SDL_RWops *context, const void *ptr, int size, int num)
+static size_t _zzip_write(SDL_RWops *context, const void *ptr, size_t size, size_t num)
 {
     return 0; /* ignored */
 }
--- a/zzip/mmapped.c
+++ b/zzip/mmapped.c
@@ -664,14 +664,14 @@ zzip_disk_entry_fopen(ZZIP_DISK * disk, ZZIP_DISK_ENTRY * entry)
     off_t offset = zzip_file_header_to_data(header);
     if (csize == 0xFFFFu) {
         struct zzip_extra_zip64* zip64 =
-           zzip_file_header_to_extras(header);
+         (struct zzip_extra_zip64*)zzip_file_header_to_extras(header);
         if (ZZIP_EXTRA_ZIP64_CHECK(zip64)) {
             csize = zzip_extra_zip64_csize(zip64);
         }
     }
     if (offset == 0xFFFFu) {
         struct zzip_extra_zip64* zip64 =
-           zzip_file_header_to_extras(header);
+           (struct zzip_extra_zip64*)zzip_file_header_to_extras(header);
         if (ZZIP_EXTRA_ZIP64_CHECK(zip64)) {
             offset = zzip_extra_zip64_offset(zip64);
         }