swift234

[SILGen] Use the signature of the real UIApplicationMain.

...instead of trying to guess it ourselves.

My previous attempt at this (part of the optional pointers work,
bc83940) made a critical mistake because our only test case /also/
referenced UIApplicationMain directly. I've made the test case test
several more situations, and also added what /would/ be an
execution test if our simulator testing handled UI-based tests.

rdar://problem/25712303