update to the latest Qt for various build improvements

- parallel OpenSSL 1.0/1.1 support
- fixes for latest MXE (mingw-w64)
- fixes for latest macOS SDK (10.13)

Also use "xcode9.3" image in TravisCI to validate the macOS build,
and switch to --openssl-linked for the Linux build.

.travis.yml

@@ -39,7 +39,7 @@ matrix:
           - libxcb1-dev
 
     - os:         osx
-      osx_image:  xcode8.3
+      osx_image:  xcode9.3
       env:        TARGET=custom-qt4-osx
 
     - os:         linux

CHANGELOG.md

@@ -18,7 +18,7 @@ v0.12.5 (unreleased)
 * add setting to perform hostname lookup via proxy (#3628)
 * correctly pass --copies to underlying QPrinter (#3747)
 * minor documentation updates and fixing compiler warnings
-* add various Qt patches to get compilation working in recent distributions
+* add various Qt patches to support OpenSSL 1.1 and latest MinGW/macOS environments
 * update OpenSSL to 1.0.2k, zlib to 1.2.11, libpng to 1.6.28 and xz to 5.2.3
 
 v0.12.4 (2016-11-22)

qt

@@ -1 +1 @@
-Subproject commit adf1539c2b775c54f398383f0d76b11b6c310564
+Subproject commit 1678f9d9ba43d202120a638f81fa1e11cff6c02c

scripts/build.py

@@ -106,7 +106,7 @@ QT_CONFIG = {
         '-xrender',                 # xrender support is required
         '-largefile',
         '-iconv',                   # iconv support is required for text codecs
-        '-openssl',                 # load OpenSSL binaries at runtime
+        '-openssl-linked',          # directly link to OpenSSL during compilation
         '-no-javascript-jit',       # can cause crashes/excess memory usage
         '-no-rpath',
         '-no-dbus',