Move alloca_.h to alloca.in.h.

diff --git a/gettext-runtime/libasprintf/alloca_.h b/gettext-runtime/libasprintf/alloca.in.h
similarity index 100%
rename from gettext-runtime/libasprintf/alloca_.h
rename to gettext-runtime/libasprintf/alloca.in.h

diff --git a/gnulib-local/lib/alloca_.h b/gnulib-local/lib/alloca.in.h
similarity index 100%
rename from gnulib-local/lib/alloca_.h
rename to gnulib-local/lib/alloca.in.h