Mark fgets() argument as UNKNOWN

If no value is passed, this reads as much as necessary, not 1024
bytes.

Author: nikic

ext/standard/basic_functions.stub.php

@@ -801,7 +801,7 @@ function feof($handle): bool {}
 function fgetc($handle): string|false {}
 
 /** @param resource $handle */
-function fgets($handle, int $length = 1024): string|false {}
+function fgets($handle, int $length = UNKNOWN): string|false {}
 
 /** @param resource $handle */
 function fread($handle, int $length): string|false {}

ext/standard/basic_functions_arginfo.h

@@ -1229,7 +1229,7 @@ ZEND_END_ARG_INFO()
 
 ZEND_BEGIN_ARG_WITH_RETURN_TYPE_MASK_EX(arginfo_fgets, 0, 1, MAY_BE_STRING|MAY_BE_FALSE)
 	ZEND_ARG_INFO(0, handle)
-	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, length, IS_LONG, 0, "1024")
+	ZEND_ARG_TYPE_INFO(0, length, IS_LONG, 0)
 ZEND_END_ARG_INFO()
 
 ZEND_BEGIN_ARG_WITH_RETURN_TYPE_MASK_EX(arginfo_fread, 0, 2, MAY_BE_STRING|MAY_BE_FALSE)