Make PLBlockIMP drop in compatible on iOS 4 and 5

[MSch]

As discussed in IRC.

[20:22] msch: now if only someone would do the work of porting MAKVONotificationCenter to use landonf's PLBlockIMP i'd be a happy man

[20:24] landonf: msch: MAKVONotificationCenter ? that should be pretty easy. Just add pl_ to the front of its blockimp function calls. Or do something like what we did in PLWeakCompatibility to co-opt the symbol names, I guess.

I haven't yet had the opportunity to test on an iOS < 4.3 device.

[landonf]

We might be picking up the AvailabilityMacros.h header via the objc headers, but it would be nice to be explicit about including the header for these defines. Also, could these #if statements be somehow combined to avoid duplicating the typedefs?

As an alternative, the code could simply skip the duplicate declarations of the imp_* APIs if the SDK's _VERSION_MAX_ALLOWED is greater than 4.3 / 10.7.

[MSch]

I think the typedefs are still necessary, because otherwise the signature of the implementation of imp_implementationWithBlock and friends is mismatched on either iOS6+ or iOS<6.

Agreed on the rest, I don't know much (anything) about the preprocessor so I went the easy and verbose route.

[MSch]

Ok, just tested on our 4.2.1 device, works flawless.

[MSch]

So, what's the plan, can this be merged? What do I have to provide in order for it to be merged? Thanks!

[landonf]

Sorry, I'm slow, but it's not off my radar :)