fix tests on 32 bits attempt.

note: using consistent "style" for test on purpose.

ext/gmp/tests/gmp_pow.phpt

@@ -2,6 +2,8 @@
 gmp_pow() basic tests
 --EXTENSIONS--
 gmp
+--SKIPIF--
+<?php if (PHP_INT_SIZE != 8) die("skip this test is for 64bit platform only"); ?>
 --FILE--
 <?php
 

ext/gmp/tests/gmp_pow_32bits.phpt

@@ -0,0 +1,77 @@
+--TEST--
+gmp_pow() basic tests
+--EXTENSIONS--
+gmp
+--SKIPIF--
+<?php if (PHP_INT_SIZE != 4) die("skip this test is for 32bit platform only"); ?>
+--FILE--
+<?php
+
+var_dump(gmp_strval(gmp_pow(2,10)));
+var_dump(gmp_strval(gmp_pow(-2,10)));
+var_dump(gmp_strval(gmp_pow(-2,11)));
+var_dump(gmp_strval(gmp_pow("2",10)));
+var_dump(gmp_strval(gmp_pow("2",0)));
+try {
+    gmp_pow("2", -1);
+} catch (ValueError $exception) {
+    echo $exception->getMessage() . "\n";
+}
+var_dump(gmp_strval(gmp_pow("-2",10)));
+try {
+    gmp_pow(20,10);
+} catch (ValueError $exception) {
+    echo $exception->getMessage() . "\n";
+}
+try {
+    gmp_pow(50,10);
+} catch (ValueError $exception) {
+    echo $exception->getMessage() . "\n";
+}
+try {
+    gmp_pow(50,-5);
+} catch (ValueError $exception) {
+    echo $exception->getMessage() . "\n";
+}
+try {
+    $n = gmp_init("20");
+    gmp_pow($n,10);
+} catch (ValueError $exception) {
+    echo $exception->getMessage() . "\n";
+}
+try {
+    $n = gmp_init("-20");
+    gmp_pow($n,10);
+} catch (ValueError $exception) {
+    echo $exception->getMessage() . "\n";
+}
+try {
+    var_dump(gmp_pow(2,array()));
+} catch (TypeError $e) {
+    echo $e->getMessage(), "\n";
+}
+
+try {
+    var_dump(gmp_pow(array(),10));
+} catch (\TypeError $e) {
+    echo $e->getMessage() . \PHP_EOL;
+}
+
+echo "Done\n";
+?>
+--EXPECT--
+string(4) "1024"
+string(4) "1024"
+string(5) "-2048"
+string(4) "1024"
+string(1) "1"
+gmp_pow(): Argument #2 ($exponent) must be greater than or equal to 0
+string(4) "1024"
+base and exponent overflow
+base and exponent overflow
+gmp_pow(): Argument #2 ($exponent) must be greater than or equal to 0
+base and exponent overflow
+base and exponent overflow
+gmp_pow(): Argument #2 ($exponent) must be of type int, array given
+gmp_pow(): Argument #1 ($num) must be of type GMP|string|int, array given
+Done