Qt5 compatibility

This commit squashes all the changes in the Qt5 branch
relative to master.

Backward compatibility with Qt4 is retained.

Original authors:

- Philip Kaufmann <phil.kaufmann@t-online.de>
- Jonas Schnelli <jonas.schnelli@include7.ch>

bitcoin-qt.pro

@@ -3,7 +3,8 @@ TARGET = bitcoin-qt
 macx:TARGET = "Bitcoin-Qt"
 VERSION = 0.8.2
 INCLUDEPATH += src src/json src/qt
-QT += network
+QT += core gui network
+greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
 DEFINES += QT_GUI BOOST_THREAD_USE_LIB BOOST_SPIRIT_THREADSAFE
 CONFIG += no_include_pwd
 CONFIG += thread
@@ -211,6 +212,7 @@ HEADERS += src/qt/bitcoingui.h \
     src/leveldb.h \
     src/threadsafety.h \
     src/limitedmap.h \
+    src/qt/macnotificationhandler.h \
     src/qt/splashscreen.h
 
 SOURCES += src/qt/bitcoin.cpp \
@@ -312,6 +314,7 @@ DEFINES += BITCOIN_QT_TEST
   macx: CONFIG -= app_bundle
 }
 
+# Todo: Remove this line when switching to Qt5, as that option was removed
 CODECFORTR = UTF-8
 
 # for lrelease/lupdate
@@ -335,6 +338,7 @@ QMAKE_EXTRA_COMPILERS += TSQM
 OTHER_FILES += README.md \
     doc/*.rst \
     doc/*.txt \
+    doc/*.md \
     src/qt/res/bitcoin-qt.rc \
     src/test/*.cpp \
     src/test/*.h \