Move inline function Bool Runtime::compareEqual() above usage.

Fix MinGW-warnings:

src/qml/jsruntime/qv4runtime_p.h:496:13: warning:
'static QV4::Bool QV4::Runtime::compareEqual(QV4::ValueRef, QV4::ValueRef)' redeclared without dllimport attribute after being referenced with dll linkage

Change-Id: Ieb212ed6aba2a0deeeddd033126ae7e9737bb38e
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>