Avoid duplicating flags/types in qmetaobjectbuilder

Avoid duplicating flags/types in qmetaobjectbuilder

Presumably the contents from qmetaobject_p.h were copied
because qmetaobjectbuilder originally lived outside of qtbase,
and private headers could not be included from other modules.
But now we can just include the right headers.

Change-Id: I975df1ea94455f1bf0db1d8024de8f5379fc9fc7
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Lorn Potter <lorn.potter@nokia.com>