Merge pull request #1 from BerndGabriel/HtmlViewer-11.4-to-11.5

Html viewer 11.4 to 11.5
Code fixes to compile in Delphi 6
Initial implementation of Progress

Only tested on Delphi 6
TProgressBar has Style from 2010. This may be in earlier versions.
Merge branch 'HtmlViewer-11.4-to-11.5' of https://github.com/MartinSedgewick/HtmlViewer.git into HtmlViewer-11.4-to-11.5
Merge branch 'ProgressBar' of https://github.com/MartinSedgewick/HtmlViewer.git into HtmlViewer-11.4-to-11.5
Fixed: cannot open form with Delphi < 2010 (unknown Touhc property)
TProgressObj for Delphi > 6