CppTools: Update visible documents on project update

With asynchron project managers, creating a new project from a wizard or
re-opening a session will first open the editor documents and then
provide the project information later (it's the other way around with
synchronous project managers). This sequence leave the documents with
various error diagnostics behind. Fixed by re-triggering the re-parsing.

This change does not fix QTCREATORBUG-11606 yet. Though it will trigger
a reparse with the right includes, clang still reports 'file not found'.
Will be addressed by a follow-up patch.

Task-number: QTCREATORBUG-11606
Change-Id: Ib5d251e05accf4268f9b36decc5224b2c75f610c
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@digia.com>
C++: Fix parsing of "Foo *foo = new Foo()"

It should be parsed as an DeclarationStatement, but instead it was
parsed as an ExpressionStatement.

Regression introduced with

    commit d3c5fff66de034e46e825b63943909d36067405f.
    C++: Fix expensive parsing of expressions

The introduced ASTCache did not save the correct return value of a
parse* function. Because of that, the first return in
Parser::parseExpressionList returned false on the second invocation
(cache hit), instead of true, which resulted in an ExpressionStatement.

Task-number: QTCREATORBUG-13122
Change-Id: I8dbd8852b0909edddcd3195b484f4cea92328cc5
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@digia.com>