Allow configurable access modifier using star

[ThomasGoulet73]

Currently, --with-access-specifier *=internal does not seem to work and I think it would be useful when you want to generate internal bindings. Passing true as the fourth parameter in the call to TryGetRemappedValue here seems to fix this issue:

ClangSharp/sources/ClangSharp.PInvokeGenerator/PInvokeGenerator.cs

Line 1814 in 82e6715

if (!TryGetRemappedValue(namedDecl, _config.WithAccessSpecifiers, out var accessSpecifier) || (accessSpecifier == AccessSpecifier.None))

I'm not very familiar with this codebase so I'll let the maintainers decide if this is the right fix and I would be happy to submit a PR.

[tannergooding]

This was resolved with #359