patch 8.0.1426: "gf" and <cfile> don't accept ? and & in URL

Problem:    "gf" and <cfile> don't accept ? and & in URL. (Dmitrii Tcyganok)
Solution:   Check for a URL and allow for extra characters. (closes #2493)
diff --git a/src/testdir/test_gf.vim b/src/testdir/test_gf.vim
index ef1bf10..c352379 100644
--- a/src/testdir/test_gf.vim
+++ b/src/testdir/test_gf.vim
@@ -7,7 +7,8 @@
       \ "first test for URL://machine.name/tmp/vimtest2a and other text",
       \ "second test for URL://machine.name/tmp/vimtest2b. And other text",
       \ "third test for URL:\\\\machine.name\\vimtest2c and other text",
-      \ "fourth test for URL:\\\\machine.name\\tmp\\vimtest2d, and other text"
+      \ "fourth test for URL:\\\\machine.name\\tmp\\vimtest2d, and other text",
+      \ "fifth test for URL://machine.name/tmp?q=vim&opt=yes and other text",
       \ ])
   call cursor(1,1)
   call search("^first")
@@ -28,6 +29,10 @@
   call search("URL")
   call assert_equal("URL:\\\\machine.name\\tmp\\vimtest2d", expand("<cfile>"))
 
+  call search("^fifth")
+  call search("URL")
+  call assert_equal("URL://machine.name/tmp?q=vim&opt=yes", expand("<cfile>"))
+
   set isf&vim
   enew!
 endfunc