Use the "gcc" feature in simd.prf

Matches the compiler capabilities better and will catch all GCC-like
compilers (including Clang, LLVM and Intel CC on Unix).

Task-number: QTBUG-38544
Change-Id: I102966d307a4e167b6dcf3da08359e656f3af45e
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Testlib: Fix minor leak and crash when comparing lists

1) toString does not track the string it returns, thus it has to be
deleted by the caller
2) on some platforms vsnprintf crashes if a null string is in the
va_list

Change-Id: Iecf94e93d3a2ddf4186ee20de1f495f2f92dcc60
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Fix FT glyph outline to path conversion

When the start point is not on the curve, the end point will be
used as starting point for the QPainterPath, if it is on the curve -
if it is not on the curve, the mid point between start and end point
will be used. The origianl start point will still be used as a control
point for the first bezier curve.

Task-number: QTBUG-38601
Change-Id: I90e07f1141288873263f1f12fa51e6a248d0804f
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Accessibility Android: Do not always append role

Task-number: QTBUG-36584
Change-Id: Id14962a9eb7a6c3ea78cefcfcc053fac886ba8f7
Reviewed-by: Jan Arve Sæther <jan-arve.saether@digia.com>
Direct2D QPA: Speed up text rendering

After analysing text drawing performance two things seem to take up most
of the time. The first is font lookup, the second is QVector
initialization.

To address the first point a per paint engine instance font cache is
introduced. At the moment no mechanism exists to clear this cache and
it is unbounded.

To address the second point, we simply switch to using QVarLengthArray
instead of QVector.

In an artificial benchmark that draws text in a tight loop, the first
change raised fps from ~70 to ~100. The second change further raised this
number to ~115 fps.

Change-Id: Iafa25c3e35bc42bd7c1582b0636e721c5193b494
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Direct2D QPA: Check Direct2D version

Since we require a relatively recent system, check the version of the
direct2d dll on disk and report an error to the user if it is too old.
Previously only a cryptic runtime error resulted from a direct2d version
that was too old.

Change-Id: I6c3955e1a98326fca6bcdc871b0a25291391ba88
Reviewed-by: Risto Avila <risto.avila@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>