Automatically type all block arguments in function definitions with Block_literal *

When parsing Objective-C and Swift function metadata, you often encounter blocks which are stack or global closures.

When you encounter these, apply a copy of the type Block_literal * to them.

struct Block_literal {
    void *isa;                    // Pointer to block's class ("isa" pointer)
    int flags;                    // Block flags
    int reserved;                 // Reserved for future use
    void (*invoke)(void *, ...);  // Function pointer to the block's code
    struct Block_descriptor *descriptor;  // Pointer to block's descriptor
    // ... captured variables (optional, not part of base header)
};

This type is the base type of all blocks in Objective-C and Swift. It will enable proper type propagation at all the call sites. The type is just the base type -- it can be further refined by parsing the Block_descriptor. I would prefer you make a copy of the block literal, because each call site will be different and we can fine the type in a second pass.

It goes a long way towards making ObjC and Swift easier to reverse

vs

The issue names no source file, test, or entry point. Start by locating the parsing of Objective-C and Swift function metadata and block literals; done means block arguments receive copied Block_literal * types and that type propagation reaches their call sites.