tools/gnulib: backport patches for gettext

tools/gnulib: backport patches for gettext

The latest versions of gettext rely on several changes to gnulib
including both changes to modules and new modules
and some previously gettext specific code being moved to gnulib.

Backport these changes in order to allow updating gettext
while using the local gnulib copy of sources.

Add patch:
 - 640-mem-hash-map.patch
 - 645-next-prime.patch
 - 646-hashcode-string.patch
 - 647-hashkey-string.patch
 - 650-package-version.patch
 - 651-package-version-simplify.patch
 - 652-package-version-simplify-further.patch
 - 653-package-version-warning.patch
 - 660-version-stamp.patch
 - 689-vc-mtime.patch
 - 755-clean-temp-hashkey.patch
 - 795-string-desc-rename-functions.patch
 - 796-vc-mtime-less-read.patch
 - 797-vc-mtime-add-api.patch
 - 798-vc-mtime-add-api.patch
 - 799-vc-mtime-old-git.patch
 - 900-str_startswith-module.patch
 - 901-str_endswith-module.patch

Signed-off-by: Michael Pratt <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/16522
Signed-off-by: Robert Marko <[email protected]>