Merge branch 'release/v006' into develop
Split function for compiling continuation
Use `int` for type name
Expand call frame for direct call/cc
Producing jumps in place of continuations #98

If a continuation is used only for exit,
omit creating continuation and
replace it with SETJMP ~ LONGJMP instructions.
Omit using SETJMP if the continuation is not used
Merge branch 'feature/setjmp' into develop
Add test for unused continuation
Remove unused function
Move code definition order
Fix indent
Add `error` function
Print "No result value" in repl
Use optimized quasiquote expander #23
Use quasiquote for defining functions
Merge branch 'feature/backquote' into develop
Use let1
Correct switching file descriptor
Stop allocating Symbol instance on `gensym` #52
Move Symbol definition from object.hh to symbol_manager.hh