apache: update InstallDev

The package doesn't need to install _everything_ to staging. This commit
reduces the amount of files that get copied over to staging. Currently
there's no package depending on apache anyway.

This adds sed scripts from buildroot (thanks!) to fix two files that are
important for cross-compiling external modules. This has been tested and
was confirmed to work with mod_gnutls taken as an example package.

Signed-off-by: Sebastian Kemper <sebastian_ml@gmx.net>