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 <simon.hausmann@digia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Fix change-of-sign warning in the new QML compiler

The m_line and m_column members are of type quint16, so -1 is not
valid. BTW, aren't 65535 possible lines too few?

qqmlboundsignal.cpp(92): error #68: integer conversion resulted in a change of sign

Change-Id: I2f73c276c5fc9b6988b5fa4274f7fa3f6bb85c4b
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Add a namespace for a global variable in a public header

The "Qml" prefix should suffice.

This was found by ICC 14.0 in a bogus warning:
qqml.h(470): error #2415: variable "CurrentSingletonTypeRegistrationVersion" of static storage duration was declared but never referenced

Change-Id: I604cd712529b1c4553457c1ea0904182ac4a9e80
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Christopher Adams <chris.adams@jollamobile.com>