Suppress error messages when checking for Direct2D availability.

Use wxDL_QUIET flag when loading Direct2D DLLs as we're prepared to handle
their absence and don't need to show error messages if they're not available.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77683 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Simplify Direct2D DLLs loading code a little.

Bail out earlier: if d2d1.dll is not there, it doesn't make sense to try to
load dwrite.dll.

Also use Load() return value directly instead of ignoring it and then checking
for IsLoaded().

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77684 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775