[SAOC 2025] Improve importC Weekly Update #4

[Emmanuel]

Hi guys,

This week, I worked on fixing issue #18057 and #21930. These were 
literally the same things.

for redeclaration, it was allowing code like


         int a;
         double a;

which was supposed to err on definition of different types.

This has been fixed.

link to PR: 
https://github.com/dlang/dmd/pull/21955#pullrequestreview-3326052849


Now, I am focused on finally fixing symbol table duplication of C 
symbols which I discovered myself, and then submit a PR for 
documentation on import paths and then set up a simple C library 
being used in D and then use that for further fixes.

Thanks!