[SAOC 2025] Improve importC Weekly Update #2

[Emmanuel]

Hi everyone,

This week, I had a long run with issue 20092 working to make 
compound literals fully work in importC and it has been 
successfully fixed and merged.

issue: https://github.com/dlang/dmd/issues/20092

The whole idea as discussed with my mentor was to create a 
temporary variable and then export it with the addressof operator 
during semantic analysis.

I did a lot of research into the expression semantics to fully 
understand how the compound literals would fit together. for 
local pointers, creating a temporary and making sure the variable 
declaration and the variable expression were exported with the 
`addressof` was enough.

for globals, it needed a little extra tinkering by making sure I 
push the symbol into the symbol table for the address to be 
picked up by the pointer.

PR : https://github.com/dlang/dmd/pull/21908#event-19961166923


`int *p = &(int){0};` in importC should get you a valid pointer 
which you can work with and not necessarily creating an object 
before pointing it as defined by the C standard.