Reserve AllDelayed vector to upper bound.
Reserve AllDelayed vector to upper bound.

File: [swift/lib/Parse/PersistentParserState.cpp]

Observing this code snipped closely in function, [void PersistentParserState::parseAllDelayedDeclLists()]:
```
for (auto &P: DelayedDeclListStates) {
    AllDelayed.push_back(P.first);
}
```

We observe that 'AllDelayed' gets maximum of DelayedDeclListStates.size() elements pushed into it.
So it is better to reserve 'vector AllDelayed' to that max size, to save reallocation cost.

I believe we can use size() on [DelayedDeclListStates], which is of type: ```llvm::DenseMap<IterableDeclContext *, std::unique_ptr<DelayedDeclListState>>``` because of the ```DenseMapIterator``` implementation of size().
[http://llvm.org/doxygen/DenseMap_8h_source.html#l00126]
jmgc/swift,JGiola/swift,practicalswift/swift,devincoughlin/swift,CodaFi/swift,roambotics/swift,gregomni/swift,devincoughlin/swift,devincoughlin/swift,atrick/swift,allevato/swift,jmgc/swift,shahmishal/swift,JGiola/swift,hooman/swift,lorentey/swift,harlanhaskins/swift,karwa/swift,amraboelela/swift,JGiola/swift,glessard/swift,shajrawi/swift,shahmishal/swift,lorentey/swift,sschiau/swift,harlanhaskins/swift,sschiau/swift,jckarter/swift,ahoppen/swift,roambotics/swift,benlangmuir/swift,ahoppen/swift,glessard/swift,devincoughlin/swift,lorentey/swift,xwu/swift,practicalswift/swift,jckarter/swift,stephentyrone/swift,ahoppen/swift,xedin/swift,lorentey/swift,xwu/swift,sschiau/swift,practicalswift/swift,shahmishal/swift,aschwaighofer/swift,benlangmuir/swift,jckarter/swift,atrick/swift,sschiau/swift,jmgc/swift,allevato/swift,xedin/swift,hooman/swift,airspeedswift/swift,shajrawi/swift,rudkx/swift,lorentey/swift,lorentey/swift,jckarter/swift,airspeedswift/swift,JGiola/swift,apple/swift,CodaFi/swift,tkremenek/swift,xedin/swift,allevato/swift,airspeedswift/swift,karwa/swift,sschiau/swift,shajrawi/swift,shahmishal/swift,allevato/swift,harlanhaskins/swift,atrick/swift,gregomni/swift,ahoppen/swift,apple/swift,xedin/swift,rudkx/swift,devincoughlin/swift,gribozavr/swift,hooman/swift,shahmishal/swift,harlanhaskins/swift,atrick/swift,benlangmuir/swift,nathawes/swift,amraboelela/swift,karwa/swift,aschwaighofer/swift,shahmishal/swift,jmgc/swift,parkera/swift,amraboelela/swift,xedin/swift,lorentey/swift,stephentyrone/swift,gribozavr/swift,CodaFi/swift,apple/swift,xedin/swift,gribozavr/swift,benlangmuir/swift,allevato/swift,jmgc/swift,parkera/swift,tkremenek/swift,airspeedswift/swift,stephentyrone/swift,lorentey/swift,CodaFi/swift,nathawes/swift,aschwaighofer/swift,parkera/swift,gregomni/swift,airspeedswift/swift,harlanhaskins/swift,practicalswift/swift,gribozavr/swift,stephentyrone/swift,tkremenek/swift,JGiola/swift,tkremenek/swift,gregomni/swift,xedin/swift,xedin/swift,aschwaighofer/swift,apple/swift,benlangmuir/swift,shajrawi/swift,karwa/swift,devincoughlin/swift,gregomni/swift,gribozavr/swift,tkremenek/swift,hooman/swift,nathawes/swift,karwa/swift,hooman/swift,nathawes/swift,aschwaighofer/swift,gribozavr/swift,atrick/swift,karwa/swift,CodaFi/swift,jckarter/swift,parkera/swift,practicalswift/swift,sschiau/swift,gribozavr/swift,shahmishal/swift,parkera/swift,allevato/swift,practicalswift/swift,benlangmuir/swift,hooman/swift,amraboelela/swift,xwu/swift,practicalswift/swift,gribozavr/swift,CodaFi/swift,parkera/swift,parkera/swift,shajrawi/swift,aschwaighofer/swift,airspeedswift/swift,shahmishal/swift,stephentyrone/swift,nathawes/swift,parkera/swift,jmgc/swift,harlanhaskins/swift,harlanhaskins/swift,aschwaighofer/swift,xwu/swift,gregomni/swift,karwa/swift,rudkx/swift,rudkx/swift,nathawes/swift,glessard/swift,rudkx/swift,apple/swift,rudkx/swift,devincoughlin/swift,JGiola/swift,sschiau/swift,shajrawi/swift,roambotics/swift,devincoughlin/swift,xwu/swift,hooman/swift,tkremenek/swift,xwu/swift,shajrawi/swift,CodaFi/swift,ahoppen/swift,glessard/swift,karwa/swift,shajrawi/swift,roambotics/swift,jmgc/swift,atrick/swift,nathawes/swift,airspeedswift/swift,ahoppen/swift,apple/swift,practicalswift/swift,xwu/swift,jckarter/swift,tkremenek/swift,stephentyrone/swift,amraboelela/swift,roambotics/swift,sschiau/swift,jckarter/swift,amraboelela/swift,roambotics/swift,stephentyrone/swift,allevato/swift,glessard/swift,glessard/swift,amraboelela/swift