Add convenience method QTextFormat::isEmpty()

Change-Id: I30e74de6853908d1fec399131637848e3c2faabe
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reduce code duplication

Change-Id: I077963fcb910fa705b087e35e99cd07436c034b1
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Make conversion of semi-transparency to opaque formats consistent

Currently the non-standard opaque formats all perform inverse premultiply
on semi transparent pixels when saving. This is only performed on RGB16
and RGB32 when explicitly converting to the formats, but not when drawing.

This patch changes the conversion to be consistent across the board so
less common formats are treated the same as the most common ones. This
also makes drawing and converting to the these formats much faster.

Task-number: QTBUG-36143
Change-Id: I877ddb1c1dbb4d2dd9b4b9192525e50375a1ae60
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>
Add support for using -isystem in qmake

This commit will make qmake use -isystem automatically for any
compilers that declare support for it for any paths that are listed in
QMAKE_DEFAULT_INCDIRS.

Change-Id: I36fefc6d5bba61671f65669f0ea42704b3c3cf31
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Don't scan system includes for dependencies and don't list them

Assume that C and C++ headers found in system paths will not change,
so we don't need to tell Make about them, nor do we need to scan their
contents either.

The previous qmake behavior matched gcc's -M switch; it now matches
the -MM switch:

       -M  Instead of outputting the result of preprocessing, output a
           rule suitable for make describing the dependencies of the
           main source file.

       -MM Like -M but do not mention header files that are found in
           system header directories, nor header files that are
           included, directly or indirectly, from such a header.

This goes hand-in-hand with our use of -isystem to pass system paths
to the compiler.

Change-Id: I3346b6da496fe6495ac89c5286d066b343116f0e
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>