Different / extra API to the original `ac-library`

[toyboot4e]

While I'd like to follow ac-libary API, some have to be different.

1. Overloaded functions segtree has two different constructors for example. The latter is called build in ac-library-hs.

   explicit segtree(int n) : segtree(std::vector<S>(n, e())) {}
   explicit segtree(const std::vector<S>& v) : _n(int(v.size())) {

   maxflow and mincostflow have two different flow functions. Ones without flow limits are not in ac-library-hs (put maxBound manually).

2. Segment tree / Lazy segment tree While C++ can pass functions as type parameters, Haskell cannot. Use some type class.

3. Any more? In addition to get and set (or read and write in vector), modify and exchange can be added.

[toyboot4e]

Current arguable namings:

• SegTree, LazySegTree: get and set -> read / write They were renamed to follow array / vector API. Or just because I wanted to do so. We can add modify and exchange if necessary.
• LazySegTree: apply overloads -> applyAt and applyIn In ac-library, they are apply and apply_range, but applyIn can sound better.
• MaxFlow: edges -> edges It creates new edges, so edges makes sense.
• MinCostFlow: edges -> edges and unsafeEdges They are actually freezeEdges and unsafeFreezeEdges, but I think the non-conventional names match MaxFlow.edges and are ok.

[toyboot4e]

I didn’t intent to add extra modules, but if I do, I would add..

• Affine2d etc. (SegAct instances)
• Monoid-based rolling hash
• Fast, efficient stimes

but maybe too much. Monoids can be added for simplicity, though.