gVim Windows - Fix for Transparent Toolbar

[Simon]

Hi.

Attached is a supplement to patch 2301 that fixes the background
colour showing through the toolbar. Thanks to John Marriott for
spotting this.

The toolbar is automatically transparent which was okay when the main
window stayed as the base button colour but not any longer now the
whole window is seamlessly filled with the editor background colour.

In light of this finding I also checked the tab bar and other gui
elements. They're unaffected. :)

This one line patch simply removes transparency from the toolbar. It
has been successfully tested on Windows 10 and Windows 8.1 in 32 and
64-bit versions.

Other options not taken were:

a) rewrite the toolbar using CreateWindowEx so it could have its own
background brush (CreateToolbarEx doesn't support that) - big work.

b) remove TBSTYLE_FLAT from the CreateToolbarEx style flags - this
works but TBSTYLE_FLAT switches on other behaviours that I didn't wish
to mess with.

--

S.