This revision includes:
  - Moving from a handwritten makefile to autotools.
  - Restructuring and cleaning up the source tree.
  - Fixing the problems that the patches in the package/mtd directory fixed.

Changes:
  - Move from generic-package to autotools-package in mtd.mk.
  - Remove no longer necessary patches.
  - Update binary locations in mtd.mk
  - Update library/header locations in mtd.mk
  - Remove MTD_ADD_MISSING_LINTL definition from mtd.mk, as it's no longer
    needed.

Tested with toolchains compiled with musl, uclibc, and glibc.

Signed-off-by: Adam Duskett <aduskett@codeblue.com>
[Thomas: additional improvements
 - introduce hidden options BR2_PACKAGE_MTD_JFFS_UTILS,
   BR2_PACKAGE_MTD_UBIFS_UTILS and BR2_PACKAGE_MTD_TESTS that match the
   ./configure options of mtd. Those hidden options select the
   appropriate dependencies checked by the configure script, and are
   selected by the existing per-tool Config.in options.
 - .mk file is changed to handle properly the new hidden options
   BR2_PACKAGE_MTD_JFFS_UTILS, BR2_PACKAGE_MTD_UBIFS_UTILS and
   BR2_PACKAGE_MTD_TESTS.
 - .mk file is changed to properly handle BR2_PACKAGE_ACL, by passing
   --with-xattr/--without-xattr.
 - remove HOST_MTD_BUILD_CMDS and HOST_MTD_INSTALL_CMDS, those are no
   longer needed since we have an autotools-package now.
 - MTD_STAGING_y and MTD_INSTALL_STAGING_CMDS are removed, we use the
   default staging installation commands, that install everything that
   is needed.
 - the MTD_TARGETS_UBI_y variable is merged into MTD_TARGETS_y, as we no
   longer need to distinguish both.
 - integck installation logic is moved into MTD_TARGETS_y.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>