Set LAPACK's html documentation into the 'pre' environment

[tobolar]

The documentation of Modelica's LAPACK functions was obviously done by copy/paste from the original LAPACK's Fortran routines, but without setting it in the HTML environment. So the rendering of the documentation is tool-dependent and, to my Dymola-restricted knowledge, messy (which doesn't mean I expect Dymola shall format this better!).
So the suggested PR sets the documentation into the pre environment to make a look of the original Ascii documentation.

Additionally, documentation was improved in:

• dgelsy_vec
• dgetrs_vec

[casella]

@tobolar can you please comment on what is the goal of this PR and suggest some reviewers? Otherwise it risks remaining stuck forever.

[maltelenz]

Good improvement, rather than relying on tools to somehow automatically detect these need special rendering.

I'm assuming the <, > replacements were done in some search and replace manner, so I didn't check them all.

[tobolar]

@tobolar can you please comment on what is the goal of this PR and suggest some reviewers? Otherwise it risks remaining stuck forever.

I have changed the description of this PR.