intl: stop using fgrep for exgettext

fgrep has been deprecated in favor of grep -F for a long time, and the
next grep release (3.8 or 4.0) will print a warning of fgrep is used.
And, the fgrep command in exgettext is no longer useful after we
migrated from SVN to Git.  Remove the fgrep command so we won't see the
warning.

gcc/po/ChangeLog:

	* exgettext: Remove unneeded fgrep command.

gcc/po/exgettext

@@ -99,7 +99,7 @@ echo "scanning for keywords, %e and %n strings..." >&2
   lang_subdirs=`echo */config-lang.in */*/config-lang.in | sed -e 's|/config-lang\.in||g'`
   { for dir in "" c-family/ common/ common/config/ common/config/*/ \
       config/ config/*/ \
-      `find $lang_subdirs -type d -print | fgrep -v .svn | sort | sed -e 's|$|/|'`
+      `find $lang_subdirs -type d -print | sort | sed -e 's|$|/|'`
     do  for glob in '*.c' '*.cc' '*.h' '*.def'
         do  eval echo $dir$glob
         done