Rename instantiateCommaSeparatedSubexpressions() to instantiateExpressions()

instantiateCommaSeparatedSubexpressions() is a clunky name, and in C++17
(with fold expressions) the function will no longer be limited to comma-
separated expressions.

Change-Id: Id242f58bb291e79cefe2b28db12dbde4bafba4ed
4 files changed