build: add Valgrind suppression file for GNU/Linux

* build-aux/linux-gnu.valgrind: New.
* build-aux/local.mk: Ship it.
* configure.ac: Use it.

build-aux/linux-gnu.valgrind

@@ -0,0 +1,16 @@
+# Linux seattle 2.6.32-5-amd64 #1 SMP Thu Mar 22 17:26:33 UTC 2012
+# x86_64 GNU/Linux
+{
+   index
+   Memcheck:Cond
+   fun:index
+   fun:expand_dynamic_string_token
+   fun:_dl_map_object
+   fun:map_doit
+   fun:_dl_catch_error
+   fun:do_preload
+   fun:dl_main
+   fun:_dl_sysdep_start
+   fun:_dl_start
+   obj:/lib/ld-2.11.3.so
+}

build-aux/local.mk

@@ -16,6 +16,7 @@
 EXTRA_DIST +=                                   \
   build-aux/cross-options.pl                    \
   build-aux/darwin11.4.0.valgrind               \
+  build-aux/linux-gnu.valgrind                  \
   build-aux/move-if-change                      \
   build-aux/prev-version.txt                    \
   build-aux/update-b4-copyright

configure.ac

@@ -230,10 +230,16 @@ case $VALGRIND:$host_os in
   '':*) ;;
   *:darwin*)
     # See README-hacking.
-    # VALGRIND+=' --suppressions=$(abs_top_srcdir)/build-aux/darwin11.4.0.valgrind'
+    # VALGRIND+='-q --suppressions=$(abs_top_srcdir)/build-aux/darwin11.4.0.valgrind'
     VALGRIND=;;
   *:*)
-    AC_SUBST([VALGRIND_PREBISON], ["$VALGRIND -q"]);;
+    suppfile=build-aux/$host_os.valgrind
+    if test -f "$srcdir/$suppfile"; then
+      VALGRIND="$VALGRIND --gen-suppressions=all"
+      VALGRIND="$VALGRIND --suppressions=\$(abs_top_srcdir)/$suppfile"
+    fi
+    AC_SUBST([VALGRIND_PREBISON], ["$VALGRIND -q"])
+    ;;
 esac
 
 AM_MISSING_PROG([AUTOM4TE], [autom4te])