fix compile compatibility with wxWidgets-2.9.4
uicore: fix cef bug with wxGTK-2.9.4

everytime the window was resized to a bigger size some of the background had to be redrawn, which resulted in the disappearing of CEF. Just redraw CEF if something happens to gcWebPanel
Merge pull request #390 from karolherbst/bug288

some wxWidgets 2.9.4 stuff