Re: Add Postgres module info

Hi Tom,

This recent patch is great but causes a small problem. It mixes designated and non-designated initializers, specifically in `PG_MODULE_MAGIC_DATA(0)`.

While this is permissible in C, when imported in C++ code (in extern "C"), it causes GCC to emit an error: `either all initializer clauses should be designated or none of them should be`.
In Clang, this is a warning: `mixture of designated and non-designated initializers in the same initializer list is a C99 extension`

I understand that this won't affect C extensions, it causes a need for an unnecessary workaround for C++ extensions. C++ extensions are, of course, not first-class-supported, but they are documented as essentially feasible (and I am exercising this successfully)

Can we amend `PG_MODULE_MAGIC_DATA` to use designated initializers exclusively? This way there will be no special-casing for C++, yet it will provide relief for its users.