Allow dynamic lock of LC_NUMERIC

Allow dynamic lock of LC_NUMERIC

When processing version strings, the radix character must be a dot even
if we otherwise would be using some other character.  vutil.c
upg_version() changes to the dot, but calls sv_catpvf() which may try to
change the character to something else.  This commit introduces a way to
lock the character to a dot around the call to sv_catpvf()

vutil.c is cpan-upstream, but already blead and cpan have diverged, so
this just updates the SHA of the new version