Support multiline strings in wxDC::DrawRotatedText() in wxMSW.

The native API doesn't support this, so do it by splitting the string into
lines manually.

Closes #9686.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75750 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/dc.h

@@ -542,6 +542,9 @@ public:
         Draws the text rotated by @a angle degrees 
         (positive angles are counterclockwise; the full angle is 360 degrees).
 
+        Notice that, as with DrawText(), the @a text can contain multiple lines
+        separated by the new line (@c '\\n') characters.
+
         @note Under Win9x only TrueType fonts can be drawn by this function. In
               particular, a font different from @c wxNORMAL_FONT should be used
               as the latter is not a TrueType font. @c wxSWISS_FONT is an