Use Qt5 by default except for Windows

Linux desktop build on Travis CI also starts using Qt5 with this CL.

BUG=#327
TEST=
REF_BUG=26887740
REF_CL=133351880
REF_TIME=2016-09-15T23:26:25-07:00
REF_TIME_RAW=1474007185 -0700

.travis.yml

@@ -52,7 +52,7 @@ env:
 before_install:
   - if [ $TRAVIS_OS_NAME == linux ]; then sudo apt-get update; fi
   - if [ $TRAVIS_OS_NAME == linux ]; then sudo apt-get install -y clang python pkg-config curl bzip2 unzip make; fi
-  - if [ $TARGET_PLATFORM == Linux ]; then sudo apt-get install -y libibus-1.0-dev libglib2.0-dev libqt4-dev libgtk2.0-dev libxcb-xfixes0-dev; fi
+  - if [ $TARGET_PLATFORM == Linux ]; then sudo apt-get install -y libibus-1.0-dev libglib2.0-dev qtbase5-dev libgtk2.0-dev libxcb-xfixes0-dev; fi
   - if [ $TARGET_PLATFORM == NaCl ]; then sudo apt-get install -y libc6-i386 lib32stdc++6; fi
   - if [ ${TARGET_PLATFORM:0:7} == Android ]; then sudo apt-get install --no-install-recommends openjdk-7-jdk openjdk-7-jre-headless libjsr305-java ant zip libc6-i386 lib32stdc++6 lib32ncurses5 lib32z1; fi
 

src/build_mozc.py

@@ -272,7 +272,14 @@ def ParseGypOptions(args):
   parser.add_option('--gypdir', dest='gypdir',
                     help='Specifies the location of GYP to be used.')
   parser.add_option('--noqt', action='store_true', dest='noqt', default=False)
-  parser.add_option('--qtver', dest='qtver', choices=('4', '5'), default='4')
+
+  default_qtver = '5'
+  # TODO(yukawa): Support Qt5 on Windows
+  if IsWindows():
+    default_qtver = '4'
+  parser.add_option('--qtver', dest='qtver', choices=('4', '5'),
+                    default=default_qtver)
+
   parser.add_option('--version_file', dest='version_file',
                     help='use the specified version template file',
                     default='data/version/mozc_version_template.bzl')

src/data/version/mozc_version_template.bzl

@@ -30,7 +30,7 @@
 
 MAJOR=2
 MINOR=18
-BUILD=2612
+BUILD=2613
 REVISION=102
 # This version represents the version of Mozc IME engine (converter, predictor,
 # etc.).  This version info is included both in the Mozc server and in the Mozc