[bug-gettext] Possible small regression in generated Makefiles from gettext-0.19 with old 'make'

[Assaf Gordon]

Hello,

I've encountered a possible error in a generated 'po/Makefile' when switching 
from gettext 0.18 to 0.19.
I hope 'getetxt' is the relevant mailing list, but if the culprit is a 
different autotools part, please let me know.

When using gettext-0.19 in a project,
then running 'configure && make' on FreeBSD 9.3 (which uses some old version of 
non-gnu make),
make will fail with "error expanding embedded variable".

It can be demonstrated with this contrived example Makefile:
====
    srcdir = .
    PACKAGE = datamash

    POFILESDEPS_ = $(srcdir)/$(DOMAIN).pot
    POFILESDEPS_yes = $(POFILESDEPS_)
    POFILESDEPS_no =
    POFILESDEPS = $(POFILESDEPS_$(PO_DEPENDS_ON_POT))

    DOMAIN=$(PACKAGE)

    POTFILES = src/datamash.c
 
    all: $(POTFILES)

    $(POTFILES): $(POFILESDEPS)
====

It seems that 'PO_DEPENDS_ON_POT' is not defined anywhere, and so expanding it 
fails with this version of 'make'.
Note that it doesn't fail with GNU Make, or with the 'bmake' found on FreeBSD 
10.1.
Adding 'PO_DEPENDS_ON_POT=no' solves the issue.

Perhaps by default it can defined as 'no', instead of non-existing/empty 
variable?


thanks,
 -assaf