po-docs: hide deprecation warnings

The build emits a lot of warnings like this:

po4a-translate is deprecated. The unified po4a(1) program is more convenient and less error prone. Once
configured, `po4a --no-update` can be used as a drop-in replacement to `po4a-translate`.
po4a::pod: A new SimplePod parser is now available.  Please consider using it instead of the current Pod
           module. If you encounter any bugs, your reports would be greatly appreciated.  To use it, add
           the following line at the top of your po4a configuration file: "[po4a_alias:Pod] SimplePod".
           You can disable this message by setting the no-warn-simple option.  Sorry for the noise, and
           thank you!

But we can suppress them with some options to the po4a tools.

Actually fixing it is tracked here:
https://github.com/libguestfs/libguestfs/issues/312

(cherry picked from virt-v2v commit
 865f1ced9fedd9c3121b44b2f3461727ce9dfadc)

Signed-off-by: Cole Robinson <crobinso@redhat.com>

po-docs/Makefile.am

@@ -42,6 +42,8 @@ SUBDIRS = $(linguas_translated)
 
 libguestfs-docs.pot:
 	cd $(top_srcdir) && $(PO4A_UPDATEPO) \
+	  --no-deprecation \
+	  -o no-warn-simple \
 	  -f pod \
 	  -M utf-8 \
 	  --package-name $(PACKAGE_NAME) \

po-docs/language.mk

@@ -188,6 +188,8 @@ virt-p2v.1: virt-p2v.pod virt-p2v-kernel-config.pod
 %.pod: $(srcdir)/../$(LINGUA).po
 	rm -f $@ $@-t
 	$(guestfs_am_v_po4a_translate)$(PO4A_TRANSLATE) \
+	  --no-deprecation \
+	  -o no-warn-simple \
 	  -f pod \
 	  -M utf-8 -L utf-8 \
 	  -k 0 \