Remove IF statement related to initial zeros in X for triangular multiplications and solves ( tbmv, tbsv, tpmv, tpsv, trmm, trmv, trsm, and trsv )

[langou]

Remove IF statement related to initial zeros in B or X for triangular multiplications and solves.
So that's: TBMV, TBSV, TPMV, TBSV, TRMV, TRSV, TRMM, and TRMV.
Note that TRMM is somewhat already done in PR #1301.
For a rationale, see discussion at #636.
There is also a few removals of IF statements for ZEROs in A(I,J) for TRSM and TRMM.

Skipping these multiplications saves FLOPs but the issues are (1) it short-circuits proper NaN propagations, and (2) it is not done consistently across variants of a routine, so a variant would propagate, while another variant would not. With this PR, all variants propagate consistently.

The changes that made me pause are the changes in TRSM from

                         TEMP = ONE/A(J,J)
                          DO 220 I = 1,M
                              B(I,J) = TEMP*B(I,J)
  220                     CONTINUE

to

                          DO 220 I = 1,M
                              B(I,J) = B(I,J)/A(J,J)
  220                     CONTINUE

See #e8785e4. On the one hand B(I,J) = B(I,J)/A(J,J) behaves better with subnormal numbers, on the other hand, we could consider that we do not want to bother with subnormal numbers on the diagonal of a triangular matrix. In any case, (1) the behavior was not consistent for all variants of TRSM and (2) the behavior of Level 3 BLAS TRSM was not consistent with the behavior of the three Level 2 BLAS triangular solvers: TRSV, TPSV and TBSV. With this PR, the behavior is consistent across the board.