SRC: use LSAME for TRANS checks in gttrs

[nakatamaho]

This PR replaces direct case-sensitive TRANS character comparisons in the GTTRS routines with LSAME.

Files updated:

SRC/sgttrs.f
SRC/dgttrs.f
SRC/cgttrs.f
SRC/zgttrs.f

Summary:

• Replace direct N/n, T/t, and C/c TRANS checks with LSAME.
• Use LSAME( TRANS, 'T' ) for the complex ITRANS branch.
• Add LSAME as a logical external function.

Validation:

• Compiled sgttrs.f, dgttrs.f, cgttrs.f, and zgttrs.f with gfortran -O2 -c.
• Ran git diff --check for the staged changes before commit.

The merge-base changed after approval.

The merge-base changed after approval.