Avoid spurious translation warnings in default "make install" (#1095)

Avoid spurious translation warnings in default "make install" (#1095)

Squid defaults to --disable-translation, but the corresponding "make
install" produces dozens of alias-link.sh warnings like these:

    WARNING: az translations do not exist. Nothing to do for: az-az
    WARNING: bg translations do not exist. Nothing to do for: bg-bg
    ...
    WARNING: vi translations do not exist. Nothing to do for: vi-vn

With this change, --disable-translation builds do not attempt to
"locate" and install/link translation-related files. The following
warning is still shown, even in explicit --disable-translation builds:

    WARNING: Translation is disabled.

This change also stops exposing --disable-translation builds to
alias-link.sh bugs that generate warnings for boilerplate statements.