libports: libc_block plugin

This plugin provides support for using a Block_session connection by
opening "/dev/blkdev".
libports: add FUSE implementation

This FUSE implementation consists of libfuse, which provides a
subset of the FUSE 2.6 API and libc_fuse, which provides support
for accessing FUSE based file system via the libc.
libports: add ntfs-3g/libntfs-3g
libports: add libc_fuse_ntfs-3g
libports: add fuse-exfat/libexfat
libports: add libc_fuse_exfat
libports: add fuse-ext2/libext2fs
libports: add libc_fuse_ext2