[bugfix] identifier=?
add srfi-27
Merge branch 'srfi-27'
drop support for rational literal
no need char conversion
support exponential literal
Merge branch 'master' into cond-expand
more detail error message on car/cdr error
generate better load error message
Merge pull request #192 from KeenS/better-load-error-message

generate better load error message
add in-library
cosmetic changes
add reader struct
read_pipe didn't satisfy reader signature
add unmatch handler
unused type alias
use int for character variables
reader by readtable
refactor comma reader
refactor boolean readers