* libSyntax: Parse member access expression.
This patch uses createNodeInPlace from syntax parsing context API to
merge an expression with its suffix to create recursive nodes such as
member access expression.
Meanwhile, this patch breaks down a signed integer or float literal to a
prefix operator expression. This expression consists of two parts: an
operator and the following expression. This makes literals like "+1" or
"-1" no different from other prefix unary expressions such as "!true".
* Generate libSyntax API
This patch removes the hand-rolled libSyntax API and replaces it with an
API that's entirely automatically generated. This means the API is
guaranteed to be internally stylistically and functionally consistent.
This will make it easier to incrementally implement syntax nodes,
while allowing us to embed nodes that we do know about inside ones
that we don't.
https://bugs.swift.org/browse/SR-4062
