swift234

[ClangImporter] When matching enum prefixes, handle plural enum names.

...so that the enumerators of this declaration:

typedef NS_OPTIONS(NSUInteger, NSKeyValueObservingOptions) {
    NSKeyValueObservingOptionNew = 0x01,
    NSKeyValueObservingOptionOld = 0x02,
    NSKeyValueObservingOptionInitial NS_ENUM_AVAILABLE(10_5, 2_0) = 0x04,
    NSKeyValueObservingOptionPrior NS_ENUM_AVAILABLE(10_5, 2_0) = 0x08
};

...come in as .New, .Old, .Initial, and .Prior. The code checks for plurals
of the form -s, -es, and -ies, which covers all of the NS_OPTIONS in our SDK.

<rdar://problem/16448966>

Swift SVN r15712