Don't connect to the same signal multiple times in wxGTK wxClipboard.

We called g_signal_connect("selection_get") in wxClipboard code each time its
AddData() method was called. This resulted in progressive but noticeable
slowdown as the handler was called more and more times.

Only connect to the handler once now.

Closes #15038.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73518 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
sAlways iInclude wx/encinfo.h from src/unix/fontutil.cpp.

We use wxNativeEncodingInfo in this file, so we always need this header, not
just when not using PCH.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73519 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Don't use ternary operator ?: with wxString and literal strings.

This results in warnings about converting string literal to (non const) C
string.

Also remove the now unneeded calls to c_str() inside wxString::Printf().

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73520 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Remove wxRTTI macro for wxComboBox from Motif port.

This is now done in src/common/combocmn.cpp.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73521 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775