Refactor: Make qam64_qam64 more compact

Use local arrays and for-loop to replace duplicated statements.
For reference, here is the table of index v.s. old local variable
qam64 qam64
psi_r_, psi_i_, a_r_, a_i_, psi_a_, a_sq_, bit_met_
 0 p7_p7    16 p3_p7    32 m1_p7    48 m5_p7
 1 p7_p5    17 p3_p5    33 m1_p5    49 m5_p5
 2 p7_p3    18 p3_p3    34 m1_p3    50 m5_p3
 3 p7_p1    19 p3_p1    35 m1_p1    51 m5_p1
 4 p7_m1    20 p3_m1    36 m1_m1    52 m5_m1
 5 p7_m3    21 p3_m3    37 m1_m3    53 m5_m3
 6 p7_m5    22 p3_m5    38 m1_m5    54 m5_m5
 7 p7_m7    23 p3_m7    39 m1_m7    55 m5_m7
 8 p5_p7    24 p1_p7    40 m3_p7    56 m7_p7
 9 p5_p5    25 p1_p5    41 m3_p5    57 m7_p5
10 p5_p3    26 p1_p3    42 m3_p3    58 m7_p3
11 p5_p1    27 p1_p1    43 m3_p1    59 m7_p1
12 p5_m1    28 p1_m1    44 m3_m1    60 m7_m1
13 p5_m3    29 p1_m3    45 m3_m3    61 m7_m3
14 p5_m5    30 p1_m5    46 m3_m5    62 m7_m5
15 p5_m7    31 p1_m7    47 m3_m7    63 m7_m7

y0
 0 y0_p_7_7   16 y0_p_3_7
 1 y0_p_7_5   17 y0_p_3_5
 2 y0_p_7_3   18 y0_p_3_3
 3 y0_p_7_1   19 y0_p_3_1
 4 y0_m_7_1   20 y0_m_3_1
 5 y0_m_7_3   21 y0_m_3_3
 6 y0_m_7_5   22 y0_m_3_5
 7 y0_m_7_7   23 y0_m_3_7
 8 y0_p_5_7   24 y0_p_1_7
 9 y0_p_5_5   25 y0_p_1_5
10 y0_p_5_3   26 y0_p_1_3
11 y0_p_5_1   27 y0_p_1_1
12 y0_m_5_1   28 y0_m_1_1
13 y0_m_5_3   29 y0_m_1_3
14 y0_m_5_5   30 y0_m_1_5
15 y0_m_5_7   31 y0_m_1_7

rho_r
 0 pi_7_7   16 pi_3_7
 1 pi_7_5   17 pi_3_5
 2 pi_7_3   18 pi_3_3
 3 pi_7_1   19 pi_3_1
 4 mi_7_1   20 mi_3_1
 5 mi_7_3   21 mi_3_3
 6 mi_7_5   22 mi_3_5
 7 mi_7_7   23 mi_3_7
 8 pi_5_7   24 pi_1_7
 9 pi_5_5   25 pi_1_5
10 pi_5_3   26 pi_1_3
11 pi_5_1   27 pi_1_1
12 mi_5_1   28 mi_1_1
13 mi_5_3   29 mi_1_3
14 mi_5_5   30 mi_1_5
15 mi_5_7   31 mi_1_7