Revert "Fix GH-15980: Signed integer overflow in main/streams/streams.c"

This reverts commit 6a04c79e41, since the
new test case apparently fails on 64bit Linux, so this needs closer
investigation.

NEWS

@@ -29,8 +29,6 @@ PHP                                                                        NEWS
 - Streams:
   . Fixed bugs GH-15908 and GH-15026 (leak / assertion failure in streams.c).
     (nielsdos)
-  . Fixed bug GH-15980 (Signed integer overflow in main/streams/streams.c).
-    (cmb)
 
 - TSRM:
   . Prevent closing of unrelated handles. (cmb)

ext/standard/tests/streams/gh15980.phpt

@@ -1,11 +0,0 @@
---TEST--
-GH-15980 (Signed integer overflow in main/streams/streams.c)
---FILE--
-<?php
-$s = fopen(__FILE__, "r");
-fseek($s, 1);
-fseek($s, PHP_INT_MAX, SEEK_CUR);
-var_dump(ftell($s) > 1);
-?>
---EXPECT--
-bool(true)

main/streams/streams.c

@@ -1354,13 +1354,8 @@ PHPAPI int _php_stream_seek(php_stream *stream, zend_off_t offset, int whence)
 
 		switch(whence) {
 			case SEEK_CUR:
-				ZEND_ASSERT(stream->position >= 0);
-				if (UNEXPECTED(offset > ZEND_LONG_MAX - stream->position)) {
-					offset = ZEND_LONG_MAX;
-				} else {
-					offset = stream->position + offset;
-				}
- 				whence = SEEK_SET;
+				offset = stream->position + offset;
+				whence = SEEK_SET;
 				break;
 		}
 		ret = stream->ops->seek(stream, offset, whence, &stream->position);