Add an option to not generate "methods" when dynamic linking

[Srlion]

I think the code part for this is in here:

rust-bindgen/bindgen/codegen/dyngen.rs

Line 176 in 50ec3ee

self.struct_implementation.push(quote! {

where would it be possible to just have like .dynamic_no_methods(true)

[emilio]

Doesn't the existing blocklisting / allowlisting methods allow you enough control over this?