when --with-lib-dir is passed to configure, push lib dir into LDFLAGS
remove usage of peek_token_n from def_expression_method_name
add doc field to sl_class_t and sl_method_t
add #doc method to Class and Method
pass doc comments through to compiler, add operands for docs to CLASS and DEFINE opcodes
expose API for getting/setting docs publicly
comment doc support!
don't use apxs to compile, it's busted on later OS X

what I have here will likely only work on OS X. todo - fix for linux, etc