Add the ability to generate programs that doesn't use condition codes.

Add the ability to generate programs that doesn't use condition codes.

ctx->Shader.EmitCondCodes determines if we use condition codes.
If not, IF statement uses first operand's X component as the condition.
Added OPCODE_BRK0, OPCODE_BRK1, OPCODE_CONT0, OPCODE_CONT1 to handle
the common cases of conditional break/continue.