doc: ptext: new/modified options

-textanchor
-fontslant
-fontweight
-filloverstroke
doc: pimage: new options

-anchor
-tintcolor -tintamount
-interpolation
-srcregion
doc: pline, polyline, path: added arrowhead options
demos: some files contained old Mac line endings (CR only)
demos: textproperties

-fontweight normal|bold
-fontslant normal|italic|oblique
-fill
-filloverstroke
-fillopacity
-stroke
-strokewidth
-strokeopacity
demos: ptext: added -textanchor
demos: added imagetint
demos: pimage: added -interpolation {none|fast|best} option
demos: pimage: -srcregion
demos: added example for pimage -width/-height and -fillopacity
demos: test linear gradient and -fillopacity
demos: added pimage: -anchor demo
demos: added gradientsalpha demo
demos: added imagealpha demo
demos: added arrowhead demos