(perl #128954) improved hints for Hurd

(a) This enables the malloc wrap also on Hurd, as used on Linux
already; Perl's own test suite passed with it, and I see no reason to
diverge from the behaviour on Linux and kFreeBSD. I'm not sure whether
it affects the ABI though, so it might be safe only for the upcoming
perl 5.24 in experimental (since that breaks the ABI anyway)

(b) This improves the reporting of the GNU libc used, so it's shown in
`perl -V` (as libc value, instead of the currently empty string).

hints/gnu.sh

@@ -10,6 +10,18 @@ libswanted="$*"
 # Debian 4.0 puts ndbm in the -lgdbm_compat library.
 libswanted="$libswanted gdbm_compat"
 
+# malloc wrap works
+case "$usemallocwrap" in
+'') usemallocwrap='define' ;;
+esac
+
+# The system malloc() is about as fast and as frugal as perl's.
+# Since the system malloc() has been the default since at least
+# 5.001, we might as well leave it that way.  --AD  10 Jan 2002
+case "$usemymalloc" in
+'') usemymalloc='n' ;;
+esac
+
 case "$optimize" in
 '') optimize='-O2' ;;
 esac
@@ -23,6 +35,32 @@ case "$plibpth" in
     ;;
 esac
 
+case "$libc" in
+'')
+# If you have glibc, then report the version for ./myconfig bug reporting.
+# (Configure doesn't need to know the specific version since it just uses
+# gcc to load the library for all tests.)
+# We don't use __GLIBC__ and  __GLIBC_MINOR__ because they
+# are insufficiently precise to distinguish things like
+# libc-2.0.6 and libc-2.0.7.
+    for p in $plibpth
+    do
+        for trylib in libc.so.0.3 libc.so
+        do
+            if $test -e $p/$trylib; then
+                libc=`ls -l $p/$trylib | awk '{print $NF}'`
+                if $test "X$libc" != X; then
+                    break
+                fi
+            fi
+        done
+        if $test "X$libc" != X; then
+            break
+        fi
+    done
+    ;;
+esac
+
 # Flags needed to produce shared libraries.
 lddlflags='-shared'