Allow QtQml to compile with ICC 14.0 with -Werror
Allow QtQml to compile with ICC 14.0 with -Werror

Third-party source contains a static variable that is only used in
debugging code (an ASSERT).

cached-powers.cc(134): warning #2415: variable "double_conversion::kCachedPowersLength" of static storage duration was declared but never referenced
  static const int kCachedPowersLength = ARRAY_SIZE(kCachedPowers);

Change-Id: I97ea9ada8f03d9fd45149fbc4bfdf61877498339
Reviewed-by: Simon Hausmann <a975102812d593b3191088e3d0aeaeb6f11dbcf5@digia.com>
Reviewed-by: Oswald Buddenhagen <6a8868beda3e139b5ac22b2534a23d3e6ba81819@digia.com>

qmlc/qtdeclarative,matthewvogt/qtdeclarative,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,matthewvogt/qtdeclarative,matthewvogt/qtdeclarative,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,qmlc/qtdeclarative,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,matthewvogt/qtdeclarative,matthewvogt/qtdeclarative,matthewvogt/qtdeclarative,matthewvogt/qtdeclarative,qmlc/qtdeclarative,matthewvogt/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative