Fix extractCurrent absolute path detection on Windows

path[0] != '/' only catches Unix absolute paths. On Windows, absolute
paths start with a drive letter (C:\) or UNC prefix (\\). Use PHP's
IS_ABSOLUTE_PATH() macro which handles all cases on both platforms.

Without this fix, setting $e->pathname to an absolute Windows path
caused the CWD to be prepended, producing a garbage path that
archive_write_header() silently failed to create.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: cataphract

libarchive.c

@@ -279,7 +279,7 @@ PHP_METHOD(libarchive_Archive, extractCurrent)
                 -1);
         return;
     }
-    if (path[0] != '/') {
+    if (!IS_ABSOLUTE_PATH(path, strlen(path))) {
         char cwd[MAXPATHLEN];
         char *result = VCWD_GETCWD(cwd, sizeof(cwd));
         if (!result) {