Bind meta wildcards to selected meta value once crate is chosen

[graydon]

In the library scanner, we should pull out any meta wildcards and bind them to the runtime meta requirements to satisfy. This way a user can say "use lib foo by symbolic name, but bind the compiled crate to whatever major.minor version of it you find"

[graydon]

Shifted to rustc.

[brson]

Doesn't this happen automatically by virtue of the linkage metadata being encoded in the filename of the library? The crate will just request use std but we will link it to libstd-0.1-ABDCE and have to use that specific version forevermore.

[graydon]

Yeah, this is now obsolete. Made sense only when we were still doing our own linkage. Note how old the bug is! Closing.