Keep LLint 64-bit on the x32 ABI

The wide-integer typedef keyed on __x86_64__, which the x32 ABI also
defines even though its long is 32-bit. That silently made LLint -- the
signed 64-bit type for byte counts and file sizes -- 32-bit on x32, so
any value past INT_MAX overflowed (a >2GB size wrapped negative and the
cache dropped the entry). Exclude __ILP32__ so x32 takes the long-long
path, plus a compile-time guard that trips wherever 64-bit support is
claimed but LLint isn't actually 64-bit.

Surfaced by the cache selftests on Debian x32: cache-writefail (oversize)
and cache-corrupt both exercise >2GB entries and failed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Xavier Roche <roche@httrack.com>

src/htsglobal.h

@@ -355,8 +355,11 @@ typedef __int64 LLint;
 typedef __int64 TStamp;
 
 #define LLintP "%I64d"
+/* x32/ILP32 sets __x86_64__ but long is 32-bit; exclude it so LLint stays
+ * 64-bit. */
 #elif (defined(_LP64) || defined(__x86_64__) || defined(__powerpc64__) ||      \
-       defined(__64BIT__))
+       defined(__64BIT__)) &&                                                  \
+    !defined(__ILP32__)
 
 typedef long int LLint;
 
@@ -373,6 +376,10 @@ typedef long long int TStamp;
 
 #endif /* HTS_LONGLONG */
 
+/* Claiming long-long support must yield a real 64-bit LLint (x32 regressed:
+   __x86_64__ set but long is 32-bit). Compile-time trip, portable to C90. */
+typedef char hts_assert_llint_is_64bit[sizeof(LLint) == 8 ? 1 : -1];
+
 #else
 typedef int LLint;