Remove capitalization when specifying include-libraries.

Remove capitalization when specifying include-libraries.

MinGW installations on case-sensitive filesystems expect
lowercase names of include-libraries and (usually) include
files.
When crosscompiling on Debian 6 (targeting MS Windows) linking
fails because mingw is looking for non-existent include-libraries.
Using lowercase names solves this.

Change-Id: Id3454f4ed8ba42b6ea93d65d9c0ce567db6712df
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>