mesa: fix a recursive display list problem

mesa: fix a recursive display list problem

This fixes an issue when compiling glCallList() into another display list
when the mode is GL_COMPILE_AND_EXECUTE.

Before, the call to glCallList() called _mesa_save_CallList() which called
neutral_CallList() which then called _mesa_save_CallList() again.  In the
end, the parent display list contained two calls to the child display list
instead of one.

Let's be on the lookout for regressions caused by this change for a while
before we cherry-pick this elsewhere.