Fix compilation with Clang and libc++ under Linux

src/plugins/platforms/xcb/qxcbsessionmanager.cpp:205:80: error: use of undeclared identifier 'ERANGE'
    while (getpwuid_r(geteuid(), &entry, buf.data(), buf.size(), &entryPtr) == ERANGE) {
src/plugins/platforminputcontexts/compose/generator/qtablegenerator.cpp:173:28: error: use of undeclared identifier 'LC_CTYPE'
    char *name = setlocale(LC_CTYPE, (char *)0);

Change-Id: Ide6f3072e9158eef412973ce0a72babb41b695f0
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

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

@@ -55,6 +55,7 @@
 #include <xkbcommon_workaround.h>
 #endif
 
+#include <locale.h> // LC_CTYPE
 #include <string.h> // strchr, strncmp, etc.
 #include <strings.h> // strncasecmp
 

src/plugins/platforms/xcb/qxcbsessionmanager.cpp

@@ -48,6 +48,7 @@
 #include <qplatformdefs.h>
 #include <qsocketnotifier.h>
 #include <X11/SM/SMlib.h>
+#include <errno.h> // ERANGE
 
 
 class QSmSocketReceiver : public QObject