Added some HTML5 placeholder support.  Note that this is only supported in some Delphi versions and only newer WinNNT OS's.

Idea from http://code.google.com/p/thtmlviewer/issues/detail?id=261&colspec=ID%20Type%20Status%20Priority%20Milestone%20Reporter%20Owner%20Summary%20Opened%20Modified along with my own research.

Conflicts:
	source/Htmlsbs1.pas
Bug Fix for:

262: 	"maxlength" attribute should be recognized in text areas
Added: Placeholders for Delphi 6..2007

Conflicts:
	source/HtmlGlobals.pas
Added: Placeholders also for Lazarus