{C,Z}LARFGP: re-scale input vector more often

[christoph-conrads]

Description

Re-scale the input vector even if X is negligibly small in norm if the imaginary part of ALPHA is nonzero. For otherwise XNORM will not be computed with a small relative error.

Checklist

• [x] The documentation has been updated.
• [x] If the PR solves a specific issue, it is set to be closed on merge.

[codecov[bot]]

Codecov Report

Attention: 10 lines in your changes are missing coverage. Please review.

Comparison is base (0a3aa4d) 0.00% compared to head (827cb8e) 0.00%.

Files	Patch %	Lines
SRC/clarfgp.f	0.00%	5 Missing :warning:
SRC/zlarfgp.f	0.00%	5 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #981 +/- ## ======================================= Coverage 0.00% 0.00% ======================================= Files 1930 1930 Lines 190421 190409 -12 ======================================= + Misses 190421 190409 -12 ```

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