The previous clipping workaround/fix is now unhelpful on some Intel graphics so lets change to enabling it only when specifically enabled with an environment variable. Intel drivers incorrectly clip new graphics buffers  https://tracker.physiomeproject.org/show_bug.cgi?id=2377 Merged from cmgui_2_7_0_plus_fixes revisions 8031 and 8032
The previous clipping workaround/fix is now unhelpful on some Intel graphics so lets change to enabling it only when specifically enabled with an environment variable.
Intel drivers incorrectly clip new graphics buffers 
https://tracker.physiomeproject.org/show_bug.cgi?id=2377
Merged from cmgui_2_7_0_plus_fixes revisions 8031 and 8032


cmiss/cmgui,cmiss/cmgui