Send amount shows minimum amount placeholder

Author: JeremyCrookshank

src/qt/bitcoinamountfield.cpp

@@ -102,7 +102,7 @@ class AmountSpinBox: public QAbstractSpinBox
         CAmount val = value(&valid);
 
         currentUnit = unit;
-
+        lineEdit()->setPlaceholderText(BitcoinUnits::format(currentUnit, m_min_amount, false, BitcoinUnits::separatorAlways));
         if(valid)
             setValue(val);
         else