mtd-utils: move libmtd source files to lib/ subdirectory

mtd-utils: move libmtd source files to lib/ subdirectory

Source files for libmtd, crc32, and fec are scattered throughout the
tree.  Move them to a central location so they can be built into a
common "libmtd.a" library used by all mtd-utils programs.

This patch only renames/deletes files and does not change the content.

Also modify the build system and source code so that libmtd.a can be built
from a "common" location (lib/).  Statically link all utilities at the top
level with libmtd.a . Minor changes to mkfs.ubifs to allow using the common
crc32 implementation.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>