Fix testsuite under various locales

When the current locale doesn't match the current voice, grep would be
surprised by the produced output and believe that this is not text, for
instance with LC_ALL=ru_RU.CP1251 we get:

  TEST      tests/language-replace.test
[...]
testing mk
grep: (standard input): binary file matches
2d1
< Translate 'пејзаж'

But we can give -a to grep so it always considers its input as text.

tests/common

     ESPEAK_DATA_PATH=`pwd` LD_LIBRARY_PATH=src:${LD_LIBRARY_PATH} \
         $VALGRIND src/espeak-ng -Xq -v ${TEST_LANG} "${TEST_TEXT}" \
         > actual.txt || exit 1
-    < actual.txt grep -E "(Translate|Found:) " | sed -e 's/ \[.*][ ]*$//g' > filtered.txt
+    < actual.txt grep -a -E "(Translate|Found:) " | sed -e 's/ \[.*][ ]*$//g' > filtered.txt
     if [ "$MESSAGE" = "Ignore" ] ; then
         diff expected.txt filtered.txt || (echo "... ignoring error" && true)
     else