Rename "meta" back to "cranelift-codegen-meta" and publish it.

It appears that having the meta directory crate be inside the codegen
directory is not enough to allow codegen to depend on it without it
being published. So, let's just publish it.

lib/codegen/meta/Cargo.toml

@@ -1,10 +1,12 @@
 [package]
-name = "meta"
+name = "cranelift-codegen-meta"
 authors = ["The Cranelift Project Developers"]
-version = "0.0.0"
+version = "0.18.0"
 description = "Metaprogram for cranelift-codegen code generator library"
 license = "Apache-2.0 WITH LLVM-exception"
-documentation = "https://cranelift.readthedocs.io/"
 repository = "https://github.com/CraneStation/cranelift"
-keywords = ["compile", "compiler", "jit"]
-publish = false
+readme = "README.md"
+
+[badges]
+maintenance = { status = "experimental" }
+travis-ci = { repository = "CraneStation/cranelift" }

lib/codegen/meta/README.md

@@ -0,0 +1,2 @@
+This crate contains the metaprogram used by cranelift-codegen. It's not
+useful on its own.