Build enhancements

Qt <4.7 is partially supported now:
 * Without Qt bindings (build.sh -without-qtbinding ...)
 * With reduced functionality (i.e. package manager won't work)

Build compatibility with STL-less Qt installations

src/laybasic/laybasic/layFileDialog.h

@@ -30,6 +30,7 @@
 #include <QObject>
 
 #include <string>
+#include <vector>
 
 namespace lay
 {

src/laybasic/laybasic/layTipDialog.h

@@ -27,6 +27,7 @@
 #include "laybasicCommon.h"
 
 #include <QDialog>
+#include <string>
 
 namespace Ui {
   class TipDialog;

src/laybasic/laybasic/layWidgets.h

@@ -31,6 +31,7 @@
 #include <QLabel>
 #include <QLineEdit>
 #include <QProxyStyle>
+#include <string>
 
 namespace db
 {