Fix doc_markdown and multiline quotes and links

tests/compile-fail/doc.rs

@@ -68,18 +68,18 @@ fn test_units() {
 //~^ ERROR: you should put `foo_ℝ` between ticks
 /// foo_💣
 /// foo_❤️
-/// [ßdummy textß][foo_ß]
-/// [ℝdummy textℝ][foo_ℝ]
-/// [💣dummy tex💣t][foo_💣]
-/// [❤️dummy text❤️][foo_❤️]
-/// [ßdummy textß](foo_ß)
-/// [ℝdummy textℝ](foo_ℝ)
-/// [💣dummy tex💣t](foo_💣)
-/// [❤️dummy text❤️](foo_❤️)
-/// [foo_ß]: dummy text
-/// [foo_ℝ]: dummy text
-/// [foo_💣]: dummy text
-/// [foo_❤️]: dummy text
+/// [ßdummy textß][foo_1ß]
+/// [ℝdummy textℝ][foo_2ℝ]
+/// [💣dummy tex💣t][foo3_💣]
+/// [❤️dummy text❤️][foo_4❤️]
+/// [ßdummy textß](foo_5ß)
+/// [ℝdummy textℝ](foo_6ℝ)
+/// [💣dummy tex💣t](fo7o_💣)
+/// [❤️dummy text❤️](foo_8❤️)
+/// [foo1_ß]: dummy text
+/// [foo2_ℝ]: dummy text
+/// [foo3_💣]: dummy text
+/// [foo4_❤️]: dummy text
 /// be_sure_we_got_to_the_end_of_it
 //~^ ERROR: you should put `be_sure_we_got_to_the_end_of_it` between ticks
 fn test_unicode() {
@@ -146,5 +146,7 @@ fn issue883() {
 
 /// `foo_bar
 /// baz_quz`
+/// [foo
+/// bar](https://doc.rust-lang.org/stable/std/iter/trait.IteratorFooBar.html)
 fn multiline() {
 }