fix pcbnew file save as problem, if previous file by same basename did not exist.  Show default file ext.

Add KiCadPcbFileExt global.

Pcbnew: Drc dialog: fix a old very minor bug.
Added: single click on an item in marker list moves the board  graphic cursor on the corresponding marker location on the board
Double clicking is not modified.

Also a minor cosmetic enhancement

Eeschema: Add hotkey 'U' to edit reference. Better filtering for  hotheys V, F, U: now the corresponding field is selected without selection list between component and the field.

All: Fix an usually unwanted behavior in kicad: When closing a dialog (mainly ERC, DRC and recently a component selection by the library viewer on a double click) the mouse release left button event (which is seen by the parent after closing the dialog, becuse it is actually made in the parent) generate an unwanted command (item selection, component place ...)
This event can be now skipped if needed by calling  EDA_DRAW_FRAME::SkipNextLeftButtonReleaseEvent() from the dialog.
Very minor other fixes

Try to fix an unwanted left mouse release button event, when closing a dialog on a click or double click,
and therefore when the mouse butoon is released in the parent window
Minor other fixes.

window which would cause the part to be parked rather than staying
in drag mode.

Library Browser tool, you have to select it in the components listbox
and then press the "Insert component into schematic" button to close the
window and return to the schematic.

The attached patch enables the selection and insertion of a component in
schematic by double clicking on it in the Library Browser component
listbox. As the double clicking should have effect only if the Library
Browser was launched to load a component in schematic, the patch checks
for NULL the m_Semaphore variable, used two distinguish the mode in
which the Library Browser is running (modal, used when inserting a
component in schematic, or non-modal).

Pcbnew: plot solder mask layer with min width value specified: algorithm modified to reduce artifacts.

Pcbnew: commit patch from Heikki Pulkkinen (via displayed with its right size and clearance during track creation/edition)

* Fix offset errors when scale factor greater is than one.
* Changed behavior of fit in page when not drawing border and
  title block to fit board outline in page.
* Fix offset errors when mirroring (still not 100% correct on MSW with
  wxWidgets 2.9.4).
* Lots of the usual code cleaning and simplifying.

Pcbvew: fix a strange bug which swap x and y values for pad offsets when reading a s expr *.kicad_pcb board file.

Polyline.cpp: fix a bad wxASSERT test which generate error messages in Debug mode when there is no error, in DEBUG mode, when filling zones with holes.

which can eliminate a subsequent call to READ_LINE::Line() for a small performance gain.