glsl/ir_builder: Add more helpers for constructing expressions

glsl/ir_builder: Add more helpers for constructing expressions

Add the following functions, each of which construct the similarly named
ir expression:
    div, round_even, clamp

    equal, less, greater, lequal, gequal

    logic_not, logic_and, logic_or

    bit_not, bit_or, bit_and, lshift, rshift

    f2i, i2f, f2u, u2f, i2u, u2i

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Signed-off-by: Chad Versace <chad.versace@linux.intel.com>