[dev-context] texexec patch (recognize pdfxtex in --version)

[Taco Hoekwater]

Hi,

Here's a one-line change from me, it makes --version correctly
identify the pdfxtex executable.

Greetings, Taco

[taco at boo web2c]$ diff ~/texmf/scripts/context/perl/texexec.pl /usr/TeX/texmf-dist/scripts/context/perl/texexec.pl

2789c2789
<          { /^\s*This is (.*pdf(|e|x)TeX.*?)$/o and $texengine = $1 ;
---
>          { /^\s*This is (.*pdf(|e)TeX.*?)$/o and $texengine = $1 ;