Bug 1585356 - Back out changeset 149a759643fb reverting CityHash changes for mingw-gcc r=froydnj

The changes made to CityHash are no longer necessary with mingw-clang, so we
can revert them to the original upstream implementation.

Differential Revision: https://phabricator.services.mozilla.com/D56991

--HG--
extra : moz-landing-system : lando

other-licenses/nsis/Contrib/CityHash/CityHash.h

@@ -29,3 +29,7 @@
 #else
 #define CITYHASH_API __declspec(dllimport)
 #endif
+
+#ifndef ssize_t
+typedef int ssize_t;
+#endif

other-licenses/nsis/Contrib/CityHash/cityhash/city.cpp

@@ -217,13 +217,13 @@ uint64 CityHash64WithSeeds(const char *s, size_t len,
 }
 
 // A subroutine for CityHash128().  Returns a decent 128-bit hash for strings
-// of any length representable in an int.  Based on City and Murmur.
+// of any length representable in ssize_t.  Based on City and Murmur.
 static uint128 CityMurmur(const char *s, size_t len, uint128 seed) {
   uint64 a = Uint128Low64(seed);
   uint64 b = Uint128High64(seed);
   uint64 c = 0;
   uint64 d = 0;
-  int l = len - 16;
+  ssize_t l = len - 16;
   if (l <= 0) {  // len <= 16
     c = b * k1 + HashLen0to16(s, len);
     d = Rotate(a + (len >= 8 ? UNALIGNED_LOAD64(s) : c), 32);