ec/ecp_nistp{224,256,521}.c: harmonize usage of __uint128_t.

Reviewed-by: NMatt Caswell <matt@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NRichard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5449)

crypto/ec/ecp_nistp224.c

@@ -40,12 +40,12 @@ NON_EMPTY_TRANSLATION_UNIT
 # include <openssl/err.h>
 # include "ec_lcl.h"
 
-# if defined(__GNUC__) && (__GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 1))
+# if defined(__SIZEOF_INT128__) && __SIZEOF_INT128__==16
   /* even with gcc, the typedef won't work for 32-bit platforms */
 typedef __uint128_t uint128_t;  /* nonstandard; implemented by gcc on 64-bit
                                  * platforms */
 # else
-#  error "Need GCC 3.1 or later to define type uint128_t"
+#  error "Need GCC 4.0 or later to define type uint128_t"
 # endif
 
 typedef uint8_t u8;

crypto/ec/ecp_nistp256.c

@@ -41,13 +41,13 @@ NON_EMPTY_TRANSLATION_UNIT
 # include <openssl/err.h>
 # include "ec_lcl.h"
 
-# if defined(__GNUC__) && (__GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 1))
+# if defined(__SIZEOF_INT128__) && __SIZEOF_INT128__==16
   /* even with gcc, the typedef won't work for 32-bit platforms */
 typedef __uint128_t uint128_t;  /* nonstandard; implemented by gcc on 64-bit
                                  * platforms */
 typedef __int128_t int128_t;
 # else
-#  error "Need GCC 3.1 or later to define type uint128_t"
+#  error "Need GCC 4.0 or later to define type uint128_t"
 # endif
 
 typedef uint8_t u8;

crypto/ec/ecp_nistp521.c

@@ -40,12 +40,12 @@ NON_EMPTY_TRANSLATION_UNIT
 # include <openssl/err.h>
 # include "ec_lcl.h"
 
-# if defined(__GNUC__) && (__GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 1))
+# if defined(__SIZEOF_INT128__) && __SIZEOF_INT128__==16
   /* even with gcc, the typedef won't work for 32-bit platforms */
 typedef __uint128_t uint128_t;  /* nonstandard; implemented by gcc on 64-bit
                                  * platforms */
 # else
-#  error "Need GCC 3.1 or later to define type uint128_t"
+#  error "Need GCC 4.0 or later to define type uint128_t"
 # endif
 
 typedef uint8_t u8;