separated builtins from other symbols

builtins now have their own symbol table and
corresponding LOADB instruction.

also fixed bug in lexer where escape sequences were not
being read properly in strings (I had to remove the
double quotes around things in lexer.l)
cleaning up struct typedefs. making builtins static.

builtin objects are now static. less to worry about
when garbage collecting later.
also added help strings and min_arg members to Luci
C library functions (like builtins).