Read the forward call indicator IE and print it into channel variable
ss7_iam_fwd_ind_hex. If this variable exists, put it in the x-header.
This implementation takes bits of A, CB, D, E, F, HG, I from the hex
value. Bits of KJ, L, P-M are not taken and set to 0.
The hex value is H-A-P-I, H is the highest bit to A, and next is P-I.
I is the lowest bit in the whole field, and H is the highest bit in
the whole field. Refer to Q.763 chapter 3.23.
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