fix scope on compiling while loop

Author: itchyny

go/_test/while.go

@@ -3,3 +3,6 @@ for b {
 for {
 	var x = 1
 }
+for {
+	var x = 1
+}

go/_test/while.vim

@@ -3,3 +3,6 @@ endwhile
 while 1
   let x = 1
 endwhile
+while 1
+  let x = 1
+endwhile

go/gocompiler.vim

@@ -561,7 +561,9 @@ function s:GoCompiler.compile_while(node)
   endif
   call self.out('for %s{', cond)
   call self.incindent("\t")
+  call self.inscope()
   call self.compile_body(a:node.body)
+  call self.descope()
   call self.decindent()
   call self.out('}')
 endfunction