This tries to fix all of the places where a diagnostic message starts
with a capital letter (other than acroynyms or proper nouns) or ends
with punctuation (other than a question mark).
This is in support of a planned change to tablegen to start diagnosing
incorrect diagnostic message styles.
* Capture reexported libraries, allowable clients, rpaths, shared cache
eligibility.
* Add support for select Xarch options.
* Add diagnostics related to capturing these options.
* Add support for verifying these attributes against what is encoded in
the dylib.
