Fix clang build for libc++

Successfully builds Qt 5.2 with:

QMAKE_CXXFLAGS_CXX11 += -std=c++11 -stdlib=libc++
QMAKE_LFLAGS_CXX11   += -stdlib=libc++ -lc++abi

against:

clang version 3.3 (tags/RELEASE_33/final)

Change-Id: I778f9410c6563e78bc77ae4c20097fa561503ba1
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

src/plugins/platforminputcontexts/compose/generator/qtablegenerator.cpp

@@ -57,6 +57,7 @@
 
 #include <string.h> // strchr, strncmp, etc.
 #include <strings.h> // strncasecmp
+#include <clocale> // LC_CTYPE
 
 TableGenerator::TableGenerator() : m_state(NoErrors),
     m_systemComposeDir(QString())

src/plugins/platforms/xcb/qxcbsessionmanager.cpp

@@ -49,6 +49,7 @@
 #include <qsocketnotifier.h>
 #include <X11/SM/SMlib.h>
 
+#include <cerrno> // ERANGE
 
 class QSmSocketReceiver : public QObject
 {