New implementation of constraint programming.

Add support for reification.

Things moved to https://github.com/dourouc05/JuCP.jl

Update macros.jl

Pass the same type of argument to the different calls to parsefun.

Restore two definitions of parse_constraint to avoid ambiguity.

LoadError: LoadError: MethodError: parse_constraint(::JuMP.var"#_error#70"{Symbol}, ::Symbol, ::Symbol, ::Expr, ::Symbol, ::Symbol) is ambiguous. Candidates:
    parse_constraint(_error::Function, sense::Symbol, args...) in JuMP at C:\Users\Thibaut\.julia\dev\JuMP\src\macros.jl:180
    parse_constraint(_error::Function, lb, lsign::Symbol, aff, rsign::Symbol, ub) in JuMP at C:\Users\Thibaut\.julia\dev\JuMP\src\macros.jl:205

Implement more closely @blegat's suggestion.

Also adapt build_constraint.

Also adapt indicator constraints.

Also adapt SD constraint.

For :call constraint, dispatch on the first argument.

Clean up.

Make tests pass.

Useless extension point.

Allow rewriting the rhs of a comparison constraint.

Bug fixing (due to MA?).

Don't break user code.

If the constraint looks like `== f(x)`, whatever f or x, the previous code would always think the function f must be known by JuMP.

Reduce diff size.

@blegat's comments.

Simplify PR wrt #2228.

Simplify PR wrt #2228.

Clean PR wrt #2229.

src/macros.jl

@@ -188,6 +188,15 @@ function parse_constraint(_error::Function, sense::Symbol, lhs, rhs)
     (sense, vectorized) = _check_vectorized(sense)
     vectorized, parse_one_operator_constraint(_error, vectorized, Val(sense), lhs, rhs)...
 end
+function parse_constraint(_error::Function, ::Val{:call}, args...)
+    return parse_constraint(_error, Val(args[1]), args[2:end]...)
+end
+
+function parse_constraint(_error::Function, sense::Val, F...)
+    sense_symbol = typeof(sense).parameters[1]
+    (sense, vectorized) = _check_vectorized(sense_symbol)
+    vectorized, parse_one_operator_constraint(_error, vectorized, Val(sense), F...)...
+end
 
 function parse_ternary_constraint(_error::Function, vectorized::Bool, lb, ::Union{Val{:(<=)}, Val{:(≤)}}, aff, rsign::Union{Val{:(<=)}, Val{:(≤)}}, ub)
     newaff, parseaff = _MA.rewrite(aff)