COMP: Fix problem with narrowing in c++11

COMP: Fix problem with narrowing in c++11

modules/core/src/arithm.cpp:345:51:
error: constant expression evaluates to 4294967295 which cannot be narrowed to type 'int' [-Wc++11-narrowing]
static int CV_DECL_ALIGNED(16) v64f_absmask[] = { 0xffffffff, 0x7fffffff, 0xffffffff, 0x7fffffff };
                                                  ^~~~~~~~~~

Converted to unsigned int.  This variable is only used to initialize a bit pattern anywhy for a 128bit type.