Bitcoin-Qt: ensure all Windows scopes use win32 as identifier

- currently we sometimes use "windows" or "win32", but as per
  http://doc.qt.digia.com/qt/qmake-advanced-usage.html, windows seems to
  be not officially supported (only win32 is mentioned there)

bitcoin-qt.pro

@@ -27,7 +27,7 @@ contains(RELEASE, 1) {
     macx:QMAKE_CFLAGS += -mmacosx-version-min=10.5 -arch i386 -isysroot /Developer/SDKs/MacOSX10.5.sdk
     macx:QMAKE_OBJECTIVE_CFLAGS += -mmacosx-version-min=10.5 -arch i386 -isysroot /Developer/SDKs/MacOSX10.5.sdk
 
-    !windows:!macx {
+    !win32:!macx {
         # Linux: static link
         LIBS += -Wl,-Bstatic
     }
@@ -96,7 +96,7 @@ contains(BITCOIN_NEED_QT_PLUGINS, 1) {
 
 INCLUDEPATH += src/leveldb/include src/leveldb/helpers
 LIBS += $$PWD/src/leveldb/libleveldb.a $$PWD/src/leveldb/libmemenv.a
-!windows {
+!win32 {
     genleveldb.commands = cd $$PWD/src/leveldb && $(MAKE) libleveldb.a libmemenv.a
 } else {
     # make an educated guess about what the ranlib command is called
@@ -113,7 +113,7 @@ QMAKE_EXTRA_TARGETS += genleveldb
 QMAKE_CLEAN += $$PWD/src/leveldb/libleveldb.a; cd $$PWD/src/leveldb ; $(MAKE) clean
 
 # regenerate src/build.h
-!windows|contains(USE_BUILD_INFO, 1) {
+!win32|contains(USE_BUILD_INFO, 1) {
     genbuild.depends = FORCE
     genbuild.commands = cd $$PWD; /bin/sh share/genbuild.sh $$OUT_PWD/build/build.h
     genbuild.target = $$OUT_PWD/build/build.h
@@ -320,7 +320,7 @@ OTHER_FILES += \
 # platform specific defaults, if not overridden on command line
 isEmpty(BOOST_LIB_SUFFIX) {
     macx:BOOST_LIB_SUFFIX = -mt
-    windows:BOOST_LIB_SUFFIX = -mgw44-mt-s-1_50
+    win32:BOOST_LIB_SUFFIX = -mgw44-mt-s-1_50
 }
 
 isEmpty(BOOST_THREAD_LIB_SUFFIX) {
@@ -347,10 +347,10 @@ isEmpty(BOOST_INCLUDE_PATH) {
     macx:BOOST_INCLUDE_PATH = /opt/local/include
 }
 
-windows:DEFINES += WIN32
-windows:RC_FILE = src/qt/res/bitcoin-qt.rc
+win32:DEFINES += WIN32
+win32:RC_FILE = src/qt/res/bitcoin-qt.rc
 
-windows:!contains(MINGW_THREAD_BUGFIX, 0) {
+win32:!contains(MINGW_THREAD_BUGFIX, 0) {
     # At least qmake's win32-g++-cross profile is missing the -lmingwthrd
     # thread-safety flag. GCC has -mthreads to enable this, but it doesn't
     # work with static linking. -lmingwthrd must come BEFORE -lmingw, so
@@ -361,7 +361,7 @@ windows:!contains(MINGW_THREAD_BUGFIX, 0) {
     QMAKE_LIBS_QT_ENTRY = -lmingwthrd $$QMAKE_LIBS_QT_ENTRY
 }
 
-!windows:!macx {
+!win32:!macx {
     DEFINES += LINUX
     LIBS += -lrt
 }
@@ -381,12 +381,12 @@ INCLUDEPATH += $$BOOST_INCLUDE_PATH $$BDB_INCLUDE_PATH $$OPENSSL_INCLUDE_PATH $$
 LIBS += $$join(BOOST_LIB_PATH,,-L,) $$join(BDB_LIB_PATH,,-L,) $$join(OPENSSL_LIB_PATH,,-L,) $$join(QRENCODE_LIB_PATH,,-L,)
 LIBS += -lssl -lcrypto -ldb_cxx$$BDB_LIB_SUFFIX
 # -lgdi32 has to happen after -lcrypto (see  #681)
-windows:LIBS += -lws2_32 -lshlwapi -lmswsock -lole32 -loleaut32 -luuid -lgdi32
+win32:LIBS += -lws2_32 -lshlwapi -lmswsock -lole32 -loleaut32 -luuid -lgdi32
 LIBS += -lboost_system$$BOOST_LIB_SUFFIX -lboost_filesystem$$BOOST_LIB_SUFFIX -lboost_program_options$$BOOST_LIB_SUFFIX -lboost_thread$$BOOST_THREAD_LIB_SUFFIX
-windows:LIBS += -lboost_chrono$$BOOST_LIB_SUFFIX
+win32:LIBS += -lboost_chrono$$BOOST_LIB_SUFFIX
 
 contains(RELEASE, 1) {
-    !windows:!macx {
+    !win32:!macx {
         # Linux: turn dynamic linking back on for c/c++ runtime libraries
         LIBS += -Wl,-Bdynamic
     }