[cc1] Add symbolic constants for dodcl()
[cc1] Add symbolic constants for dodcl()

Dodcl() has 4 parameters, and having a 0 or 1 in the first was
not clear at all. These new constants add a bit of information
about the proposal of the parameter.

k0gaMSX/scc,k0gaMSX/scc,k0gaMSX/scc