[GNU] Add line marker directive

preprocess.c

@@ -839,6 +839,11 @@ static Token *preprocess2(Token *tok) {
       continue;
     }
 
+    if (tok->kind == TK_PP_NUM) {
+      read_line_marker(&tok, tok);
+      continue;
+    }
+
     if (equal(tok, "error"))
       error_tok(tok, "error");
 

test/line.c

@@ -12,6 +12,10 @@ int main() {
 #line 1
   ASSERT(2, __LINE__);
 
+# 200 "xyz" 2 3
+  ASSERT(201, __LINE__);
+  ASSERT(0, strcmp(__FILE__, "xyz"));
+
   printf("OK\n");
   return 0;
 }