e2fsprogs: change the so-version of libcom_err to prevent conflicts, move it into the libext2fs package, get rid of the pthread dependency

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@37076 3c298f89-4303-0410-b956-a3cf2f4a3e73