When lint identifies an unknown symbol, attempt to correct it if it is miscapitalized

Summary:
Ref T13598. If you spell a symbol like "Polygon" as "PoLyGoN", you currently get an "unknown symbol" lint message. However, provided "Polygon" is a valid symbol, we can unambiguously correct the spelling of the symbol.

Note that this patch can only correct the spelling of application symbols, not builtin symbols (since none of the library maps contain builtin symbols).

Test Plan:

Maniphest Tasks: T13598

Differential Revision: https://secure.phabricator.com/D21537