December 15[SAOC 25] improve importC weekly update 14

[Emmanuel]

Hi all,

this week I focused on compiling the s7 library. it's a library 
heavily dependent on complex code and I believe getting it 
successfully compiled could be a statement of success for importC 
at least with C complex.

I encountered lots of compiler time errors which I have been able 
to break them down into smaller and understandable forms.

issue 1: https://github.com/dlang/dmd/issues/22247
issue 2: https://github.com/dlang/dmd/issues/22259

last week I opened this PR to convert importC from using complex 
library struct to use the fundamental complex type.
link to PR: https://github.com/dlang/dmd/pull/22238

apparently, the conversions I have made so far in the above PR 
automatically fixed all the issues I have opened. I am still 
fleshing one last issue I am getting when compiling s7 library to 
help me break it down and test it.