Fix FNV variant in comments: this is FNV-1, not FNV-1a

The implementation uses multiply-then-XOR order, which is FNV-1.
FNV-1a would XOR first, then multiply. The constants (offset_basis
and prime) are the same for both variants; only the operation order
differs. Fix comments in cc_stubs.c, CCInt.ml, and CCHash.ml.

No behavioral change — just correcting the documentation.

src/core/CCHash.ml

@@ -7,7 +7,7 @@ type 'a t = 'a -> hash
 type 'a iter = ('a -> unit) -> unit
 type 'a gen = unit -> 'a option
 
-(* FNV hashing
+(* FNV-1 hashing (multiply then XOR)
    https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
 *)
 let fnv_offset_basis = 0xcbf29ce484222325L

src/core/CCInt.ml

@@ -4,7 +4,7 @@ include Int
 
 type 'a iter = ('a -> unit) -> unit
 
-(* use FNV:
+(* use FNV-1:
    https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function *)
 external hash : (int[@untagged]) -> (int[@untagged])
   = "caml_cc_hash_int_byte" "caml_cc_hash_int" [@@noalloc]

src/core/cc_stubs.c

@@ -1,9 +1,14 @@
 #include <caml/mlvalues.h>
 #include <stdint.h>
 
-/* FNV-1a hash for a 64-bit integer.
+/* FNV-1 hash for a 64-bit integer.
    https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
 
+   FNV-1 order: multiply then XOR (as opposed to FNV-1a which XORs first).
+   Uses the standard 64-bit FNV parameters:
+     offset_basis = 0xcbf29ce484222325
+     prime        = 0x00000100000001b3
+
    Core routine: operates on all 8 bytes of an int64_t. */
 
 static inline int64_t cc_fnv_hash_int64(int64_t n) {