comparison operators declare wrong result_type

Hi,

In functional/operators.hpp we have

`BOOST_COMPUTE_DECLARE_BINARY_OPERATOR(equal_to, "==", T, T)
BOOST_COMPUTE_DECLARE_BINARY_OPERATOR(not_equal_to, "!=", T, T)
BOOST_COMPUTE_DECLARE_BINARY_OPERATOR(greater, ">", T, T)
BOOST_COMPUTE_DECLARE_BINARY_OPERATOR(less, "<", T, T)
BOOST_COMPUTE_DECLARE_BINARY_OPERATOR(greater_equal, ">=", T, T)
BOOST_COMPUTE_DECLARE_BINARY_OPERATOR(less_equal, "<=", T, T)`

declaring a return type T of those functions. Note that the opencl specs says in 6.3 d) (among other things):

> The relational operators greater than (>), less than (<), greater than or equal (>=), and less than or equal (<=) operate on scalar and vector types. If the source operands are a vector float, the result is a vector signed integer.
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