qt 4.8.6

Bump version to [recent stable release on April 24th](http://blog.qt.digia.com/blog/2014/04/24/qt-4-8-6-released/?utm_source=rss&utm_medium=rss&utm_campaign=qt-4-8-6-released).

Removed `-no-ssse3` workaround for [QTBUG-24773](https://bugreports.qt-project.org/browse/QTBUG-24773), otherwise ended up with error like [QTBUG-38455](https://bugreports.qt-project.org/browse/QTBUG-38455) (similar on 10.7.5). Apparently, [SSE discovery was fixed](http://download.qt-project.org/official_releases/qt/4.8/4.8.6/changes-4.8.6).

Compiled fine on 10.7.5, but not tested on other OS versions.

```
$ brew --config 
HOMEBREW_VERSION: 0.9.5
ORIGIN: https://github.com/Homebrew/homebrew.git
HEAD: e8b2e3aa5c707da4e1f125d45e1faec7bd5757a5
HOMEBREW_PREFIX: /usr/local/osgeo4mac
HOMEBREW_CELLAR: /usr/local/osgeo4mac/Cellar
CPU: 8-core 64-bit sandybridge
OS X: 10.7.5-x86_64
Xcode: 4.6.3
CLT: 4.6.0.0.1.1365549073
LLVM-GCC: build 2336
Clang: 4.2 build 425
X11: 2.6.5 => /usr/X11
System Ruby: 1.8.7-358
Perl: /usr/bin/perl
Python: /usr/local/osgeo4mac/bin/python => /usr/local/osgeo4mac/Cellar/python/2.7.6_1/Frameworks/Python.framework/Versions/2.7/bin/python2.7
Ruby: /usr/bin/ruby => /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby

```