package/gettext-tiny: support gettext 0.20.1

Other changes:
  - Update gettext to 0.20.1 and the respective hashes.
  - Remove share/gettext-tiny/m4/lock.m4 from GETTEXT_TINY_EXTRA_GETTEXT_FILES
    and the install list, as this file was removed in commit
    8c2bfdbddb13a480d88ceac4ab0e5886bda957cb.

Tested with test-pkg -p gettext-tiny in Debian 10 and Centos 7

            br-arm-full [1/6]: OK
 br-arm-cortex-a9-glibc [2/6]: OK
  br-arm-cortex-m4-full [3/6]: OK
         br-x86-64-musl [4/6]: OK
     br-arm-full-static [5/6]: OK
           sourcery-arm [6/6]: OK

Signed-off-by: Adam Duskett <Aduskett@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>