Separated tokens (TOK_*) and opcodes (F_*).

Tokens are still generated by language.yacc,
while opcodes are now defined in opcodes.h.
This should make less files depend on language.yacc,
and make it possible to stabilize the opcode encoding.

Rev: src/array.c:1.71
Rev: src/builtin_functions.c:1.274
Rev: src/cpp.c:1.63
Rev: src/docode.c:1.73
Rev: src/language.yacc:1.185
Rev: src/las.c:1.179
Rev: src/lex.c:1.80
Rev: src/lexer.h:1.17
Rev: src/mapping.c:1.83
Rev: src/opcodes.h:1.6
Rev: src/peep.c:1.33
Rev: src/pike_types.c:1.130
Rev: src/program.c:1.237