Doc: Move XML example documentation to correct location

Moving the examples documentation to resolve doc linking
issues.

Task-number: QTBUG-34749
Change-Id: I2adb1b5d37911c7df6a78a03741d3d43ab24eafb
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
Doc: corrected broken links

Task-number: QTBUG-34749

Corrected link to drag and drop example.
Corrected link to {mandatory fields}
Created target referring to macros for defining plugins

Change-Id: I387a2d9bab428b2eacd8d371f08c72f42f7e2be2
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
Fixed another assert in qwindowskeymapper

When we get a WM_CHAR message we do not need to add anything to the key
map as these messages already contain the character code in question.

Task-number: QTBUG-35532

Change-Id: If73993cd873b7c616876b9ba52ceba6b27a6a7b1
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>