[ChangeLog][QtCore] Added qEnvironmentVariable, which returns the value
of an environment variable in a QString, while qgetenv continues to be
used to return it in a QByteArray. For Unix, since most environment
variables seem to contain path names, qEnvironmentVariable will do the
same as QFile::decodeName, which means NFC/NFD conversion on Apple OSes.
I opted not to #include <qfile.h> from qglobal.cpp to implement that
QFile::decodeName functionality, so qglobal.cpp doesn't depend on
corelib/io and to avoid possible recursions.
Task-number: QTBUG-41006
Change-Id: I14839ba5678944c2864bffff141794b8aaa7aa28
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
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