Add ui test for command line lints with tool names

This adds a ui test to make sure rustc accepts lint arguments such as
`-A clippy::foo` when clippy is disabled.

Author: eholk

src/test/ui/lint/command-line-register-lint-tool.rs

@@ -0,0 +1,7 @@
+// compile-flags: -A known_tool::foo
+// check-pass
+
+#![feature(register_tool)]
+#![register_tool(known_tool)]
+
+fn main() {}

src/test/ui/lint/command-line-register-unknown-lint-tool.rs

@@ -0,0 +1,4 @@
+// compile-flags: -A unknown_tool::foo
+// check-fail
+
+fn main() {}

src/test/ui/lint/command-line-register-unknown-lint-tool.stderr

@@ -0,0 +1,11 @@
+error[E0602]: unknown lint: `unknown_tool::foo`
+   |
+   = note: requested on the command line with `-A unknown_tool::foo`
+
+error[E0602]: unknown lint: `unknown_tool::foo`
+   |
+   = note: requested on the command line with `-A unknown_tool::foo`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0602`.