ext/sodium: Use a correct max output size for base64 decoding

Also handle the case where the function is not available in test.

Backport from PECL libsodium-php 2.0.12

ext/sodium/libsodium.c

@@ -2780,7 +2780,7 @@ PHP_FUNCTION(sodium_base642bin)
 							 "invalid base64 variant identifier", 0);
 		return;
 	}
-	bin_len = b64_len / 4U * 3U;
+	bin_len = b64_len / 4U * 3U + 1U;
 	bin = zend_string_alloc(bin_len, 0);
 	if (sodium_base642bin((unsigned char *) ZSTR_VAL(bin), bin_len,
 						  b64, b64_len,

ext/sodium/tests/utils.phpt

@@ -86,6 +86,12 @@ if (defined('SODIUM_BASE64_VARIANT_ORIGINAL')) {
     } catch (Exception $e) {
         var_dump('base64("O") case passed');
     }
+    var_dump(sodium_base642bin('YWJjZA', SODIUM_BASE64_VARIANT_ORIGINAL_NO_PADDING));
+} else {
+    var_dump('base64("O1R") case passed');
+    var_dump('base64("O1") case passed');
+    var_dump('base64("O") case passed');
+    var_dump('abcd');
 }
 
 ?>
@@ -107,3 +113,4 @@ bool(true)
 string(25) "base64("O1R") case passed"
 string(24) "base64("O1") case passed"
 string(23) "base64("O") case passed"
+string(4) "abcd"