docs: Fix StudlyCaps in libxc-migration-stream.pandoc and xl.1.pod

docs: Fix StudlyCaps in libxc-migration-stream.pandoc and xl.1.pod

$ git-grep libxenctrl | wc -l
99
$ git-grep libxc | wc -l
206
$ git-grep libxenlight | wc -l
48
$ git-grep libxl | wc -l
13433
$ git-grep LibXen | wc -l
2
$

Reported-by: Paul Durrant <pdurrant@amazon.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Wei Liu <wl@xen.org>