[platform-text-dev] jdt-ui head needs head of jface.text, text, and ui.w

[Tom Eicher <eclipse@xxxxxxxxxxxxxxx>]

Moved linked position infrastructure to text components.

In order to compile jdt.ui HEAD, head of

org.eclipse.jface.text
org.eclipse.text
org.eclipse.ui.workbench.texteditor

are needed.

Additionally, HEAD of ui.workbench.texteditor depends on HEAD of 
jface.text, which needs HEAD of text in return.

-tom