rustc: use Name numbers rather than the Show impl for constants.

Using the Show impl for Names created global symbols with names like
`"str\"str\"(1027)"`. This adjusts strings, binaries and vtables to
avoid using that impl.

Fixes #15799.

src/test/run-make/symbols-are-reasonable/Makefile

@@ -0,0 +1,15 @@
+-include ../tools.mk
+
+# check that the compile generated symbols for strings, binaries,
+# vtables, etc. have semisane names (e.g. `str1234`); it's relatively
+# easy to accidentally modify the compiler internals to make them
+# become things like `str"str"(1234)`.
+
+OUT=$(TMPDIR)/lib.s
+
+all:
+	$(RUSTC) lib.rs --emit=asm --crate-type=staticlib
+	# just check for symbol declarations with the names we're expecting.
+	grep 'str[0-9]\+:' $(OUT)
+	grep 'binary[0-9]\+:' $(OUT)
+	grep 'vtable[0-9]\+' $(OUT)

src/test/run-make/symbols-are-reasonable/lib.rs

@@ -0,0 +1,20 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub static X: &'static str = "foobarbaz";
+pub static Y: &'static [u8] = include_bin!("lib.rs");
+
+trait Foo {}
+impl Foo for uint {}
+
+pub fn dummy() {
+    // force the vtable to be created
+    let _x = &1u as &Foo;
+}