change pic_find_rename API
Revert "reserve the 0 symbol for system use"

This reverts commit 816343bd31628180e5118ef8f093e61dc2f138b6.

Conflicts:
	include/picrin/value.h
	src/state.c
[refactor] analyze_define
[refactor] add analyze_declare
cleanup. move analyze_lambda
when procedual-define is analyzed, don't create a lambda expression
inside, call analyze_procedure directly instead.
get rid of redundant symbol to value cast
Merge branch 'refactor-analyzer'