[LyX/master] #9323 add check for Qt5MacExtras to use it on Mac with --enable-qt5

[Stephan Witt]

commit 0379bade176f70f6edfe5541b6ea07c64dace6be
Author: Stephan Witt <sw...@lyx.org>
Date:   Mon Dec 29 00:18:40 2014 +0100

    #9323 add check for Qt5MacExtras to use it on Mac with --enable-qt5

diff --git a/config/qt4.m4 b/config/qt4.m4
index 10d9546..aa94ae9 100644
--- a/config/qt4.m4
+++ b/config/qt4.m4
@@ -206,6 +206,10 @@ AC_DEFUN([QT_DO_PKG_CONFIG],
                if $lyx_use_winextras; then
                        qt_guilibs="$qt_guilibs Qt5WinExtras"
                fi
+               PKG_CHECK_EXISTS(Qt5MacExtras, [lyx_use_macextras=true], [])
+               if $lyx_use_macextras; then
+                       qt_guilibs="$qt_guilibs Qt5MacExtras"
+               fi
        fi
        PKG_CHECK_MODULES(QT_CORE, $qt_corelibs,,[:])
        if test "$pkg_failed" = "no" ; then