Option to require a list symbols to be defined when linking

[AngheloAlf]

If you want to make sure certain file gets linked then you add a symbol of that file into this list.

For example, requiring the guMtxCatL symbol would emit the following:

EXTERN(guMtxCatL);
ASSERT(DEFINED(guMtxCatL), "Error: guMtxCatL was not linked");