fix(to_cpp1): direct-initialize statement parameter and constexpr variable

[JohelEGP]

Resolves #699. Resolves #801.
Resolves #527.

[hsutter]

Thanks! I see this also fixes another annoyance that I hadn't yet got around to fixing, which was initializing something like a vector in a statement parameter list:

(v: std::vector<int> = (1,2,3))   // miscompiles today, works with this PR
for v do (e) std::cout << e;