Log Message:
libcap: update to 2.44

Set prefix variable in MAKE_FLAGS so that the *.pc files use the
correct paths.

Use gsed tool since -i flag is used during build.

Disable Go library.

Skip portability check of contrib/pcaps4server; it is not installed
or used during build.

Upstream release notes:
https://sites.google.com/site/fullycapable/release-notes-for-libcap#h.bkhhw1fow1su