upgrade xvect.h
eliminate uses of '__'
avoid import error not propagated to the toplevel
add pic_import_library
move pic_std* prototypes to picrin.h
huge improvement of README
change actual type of pic_sym
move debug prints in the VM
don't use dictionaries as import_table
remove debug print
dictionary is now a equal?-based hash table
[bugfix] plist<->dictionary broken
add missing quote
Merge pull request #30 from picrin-scheme/object-dictionary

Object-to-object dictionary
pic_var_push and pic_var_pop are private APIs
add pic_defined_p
add definition of pic_set
refactor parameter. var data structure is no longer used
implement parameterize
[bugfix] funcall doesn't take a module to run