implement memq and assq with c
implement memv and assv with C
Merge branch 'memq-in-c'

Conflicts:
	piclib/prelude.scm
unlock testable cases
fix a bug of plus reader
Merge pull request #172 from KeenS/plus-reader

fix a bug of plus reader
Merge pull request #171 from KeenS/test

unlock tastable cases
share cache between wrap and inject
add walk-symbol
walk-symbol by default
add memoize function
fix a bug in walk function
inline some trivial functions
Merge branch 'ir-refactor'
vector-map is no longer used
change init_contrib API
update gitignore
maintain exports table as a dict
add library-exports