publish struct pic_escape
add make_escape
missing validation flag change
publish continuation internal APIs
refactor pic_push_try. use raw continuation API
mark invalid flag
s/pic_make_cont/pic_make_econt/g
add many many assertions (pic_pop_try)
don't do pop_try when an error was raised
add noreturn mark
don't setjmp in pic_save_point
don't setjmp in pic_push_try
don't perform longjmp in pic_load_point (for the symmetry)
Merge branch 'fix-try-catch'