Pcbnew: fix  compil warning and a minor bug in plot negative (frame fer plotted in white therefore not visible).
minor code cleaning

only for Pcbnew in Decimils version. These definitions are provided, but not yet used in code.

Pcbnew, plot functions: fix bug in SVG plotter, fix a minor other bug when using PS plotter (trcak width fine adjust not working)
and plot code cleaning continued

All: remove macros  MAX, MIN, ABS from macros.h and replace these macros by std::max, std::min and std::abs (mainly found in old code).

switch all <math.h> includes to <cmath> includes on an attempt to dodge some abiguous references to atan2()

dcsvg (and therefore KicadSVGFileDC)  is now unused. Use SVG plotter only to export a board SVG file.
SVG export does not use no more wxWidgets wxDC.
In pcbnew SVG files can be created by plot menu (in B&W) or export SVG menu (B&W or Color).
Export SVG menu is more suitable to create a view of a board, and plot menu is better to create a B&W document of silkscreen layers.
(In the future, the 2 menus could be merged, because they are not very different).
Note: pcbnew plot code is cleaned, mainly in dialog files, but still needs more cleanup.

SVG plotter: fix issues in draw arc and draw rectangle.

Eeschema: Plot dialogs: unify 5 dialogs (which means 5 duplicate code) to only one plot dialog (like in Pcbnew)
remove duplicate code and clean it.
Simplify HPGL dialog: plot offet removed and replaced by only one option:
plot origin to center of sheet or not (some HPGL  plotters have the plot origin to center of the paper area,
and others have this origin at the bottom left corner)
This is surely enough.

Eeschema: Plot dialogs: unify 5 dialogs (which means 5 duplicate code) to only one plot dialog (like in Pcbnew)
clean duplicate code.
Simplify HPGL dialog: plot offet removed and replace by only one option (plot origin to center of sheet or not)
This is surely enought.

Mainly to plot drill maps, but can be used to plot boards, for documentation.
The print svg still exists, but the plot SVG has more options (mirroring, holes in pads),
however  print svg allows color print, and full board printing, and plot does not.

Pcbnew: fix minor issue when loading a foorprint: if the footprint name has lower case letters, the name was asked twice

All: fix some Doxygen warnings

Other minor fixes.