Fix some warnings

[rootkea]

Hello!

This PR fixes some warnings like:

../app/src/util/vecdeque.h:193:24: warning: arithmetic on a pointer to void is a GNU extension [-Wpointer-arith]
    memcpy(newptr, ptr + (oldorigin * item_size), right_len * item_size);
                   ~~~ ^
../app/src/util/vecdeque.h:196:23: warning: arithmetic on a pointer to void is a GNU extension [-Wpointer-arith]
        memcpy(newptr + (right_len * item_size), ptr,
               ~~~~~~ ^
...
../app/src/server.c:303:45: warning: empty expression statement has no effect; remove unnecessary ';' to silence this warning [-Wextra-semi-stmt]
        ADD_PARAM("downsize_on_error=false");

[rom1v]

Thank you 👍 Merged into dev:

• 0bbe8a7
• 8cef8ba (I added more missing statics, and I added a commit to warn about them)
• bc8913e