Support for anonymous nested record

[Gnimuc]

Since Julia doesn't support defining nested structs:

struct Foo
    struct Bar
         b
    end
    x::Bar  # x can't see Bar
end

the workaround used here is to define a global hard-coded mangling "anonymous" struct and then treat it as a common struct when generating ASTs.

• nested union fix Support for typedef union #222
• nested struct
• add warning message for no method value(::CLPackedAttr) #224

[vchuravy]

I found two cases were this branch did mostly the right thing: #222 (comment)

[Gnimuc]

For #224, should we generate code for __attribute__ enums with a warning message or not generate code at all?

[vchuravy]

Looks good from my side the generated files look reasonable.

[Gnimuc]

merged and tagged v0.8.2.