Add test for removed one character last line in rustdoc

src/test/rustdoc/include_str_cut.rs

@@ -0,0 +1,7 @@
+#![crate_name = "foo"]
+#![no_std]
+
+// @has 'foo/fn.foo.html'
+// @has - '//*[@class="docblock"]' 'inc2 x'
+#[doc = include_str!("short-line.md")]
+pub fn foo() {}

src/test/rustdoc/short-line.md

@@ -0,0 +1,2 @@
+inc2
+x