ex 5.10 - skipped
ex 5.11 - done
ex 5.12 - done
ex 5.13 - extend to support "*"
ex 5.13 - done
ex 5.14 - not working
ex 5.15, 5.16 - skipped
implement trampoline interpreter
remove unused files
make it a template program
ex 5.17 - done
ex 5.18 - done
ex 5.19 - wrap apply-cont
ex 5.19 - done
trampoline template, remove some trailing spaces
skip ex 5.21 and ex 5.22
Merge branch 'eopl'