mirror fixes for fdo#78906 and deb#766788 into icu

(cherry picked from commit a66451887425ddd9387e2b25d5125916f4a35f83)
(cherry picked from commit bff0fe902686d8c126a73e1d2c914f5d65c6ffaf)

Conflicts:
	external/icu/UnpackedTarball_icu.mk

Change-Id: I9325bb28eb267b023f628e24fea216ad580759e9
(cherry picked from commit c0d9f573b1200f8860f1c1c89107d54226869f56)
Reviewed-on: https://gerrit.libreoffice.org/13242
Reviewed-by: Michael Stahl <mstahl@redhat.com>
Reviewed-by: Eike Rathke <erack@redhat.com>
Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>
Tested-by: Norbert Thiebaud <nthiebaud@gmail.com>