astgen: update a handful of expression types to new mem layout

break, continue, blocks, bit_not, negation, identifiers, string
literals, integer literals, inline assembly

also gave multiline string literals a different node tag from regular
string literals, for code clarity and to avoid an unnecessary load from
token_tags array.
c2b4d51749Andrew Kelley committed on 2/14/2021, 4:40:12 AMparent24798b8
4 files changedLine totals unavailable