There's a loop over nodes, calling SwTextNode::Hyphenate() each time.
Introduce a new class SwInterHyphInfoTextFrame that is used in the
SwTextFrame functions, and SwTextNode::Hyphenate() converts between
the 2 types.

Not sure if this will hyphenate a word that is split across nodes in the
model, but perhaps this is good enough in practice.

Change-Id: I78dec370e15c372284c934d9658b2dd5b3b97ae0