`struct` within `sizeof` gets incorrect scopes

[alexr00]

Checklist

• This problem exists even with the setting "C_Cpp.enhancedColorization": "Disabled"

If Disabling that^ makes the problem go away, then follow this to make an issue on the C++ extension:
https://github.com/microsoft/vscode-cpptools/issues/new/choose

The code with a problem is:

struct sigaction setup_action;
memset(&setup_action, 0, sizeof(struct sigaction));

It looks like:

Here, the struct within the sizeof has the scopes:

meta.arguments.operator.sizeof
source.cpp

Nothing there to indicate that this is struct.

It should look like:

This is when the language is set to C. The struct is highlighted correctly.

Originally from @su8 in microsoft/vscode#243001