Fix regressions

[chung-leong]

• Optional constructor
• Error union constructor
• Function constructor
• Opaque in packed struct
• Opaque constructor
• Function returning slice of slices
• Returning self-referencing struct
• Returning same struct
• Recursive structure
• Returning multiple pointers
• Returning C pointers
• Calling printf()
• Passing generator to callback
• Returning allocator
• Allocating generator returning strings
• Thread with abort signal
• Initialiization of work queue
• Read/write lock
• Union iterator
• Opaque iterator
• Stream operation using std.fs.File and std.fs.Dir
• Syscall redirection
• Reading stdin using C functions
• ArrayBuffer