complibs/ppl: fix 0.11-0.11.2 to compile with --disable-shared

PPL 0.11 (through 0.11.2) had a small bug where it still tried to build
and test its Java interface even when shared libraries are disabled.
Since that's exactly what ct-ng does, it explodes.

This is the patch from the PPL authors (see final link below).

More information can be found in these messages/threads:

Anthony's initial report and analysis with Yann:
http://www.cygwin.com/ml/crossgcc/2011-05/msg00046.html

Ron Flory hit the same problem:
http://www.cygwin.com/ml/crossgcc/2011-05/msg00054.html

Anthony's report to the ppl-devel list:
http://www.cs.unipr.it/pipermail/ppl-devel/2011-May/017450.html

Roberto's reply with a link to the fix in the PPL git repo:
http://www.cs.unipr.it/pipermail/ppl-devel/2011-May/017455.html

Signed-Off-By: Anthony Foiani <anthony.foiani@gmail.com>

Correctly check for g++ existence.

Copyright 2007 Yann E. MORIN <yann.morin.1998@anciens.enib.fr>

Licensed to you as dmalloc-5.5.2 is.

diff -dur dmalloc-5.5.2.orig/configure dmalloc-5.5.2/configure

--- dmalloc-5.5.2.orig/configure	2007-05-18 11:40:31.000000000 +0200

+++ dmalloc-5.5.2/configure	2007-05-18 11:42:02.000000000 +0200

@@ -2643,7 +2643,7 @@

 # see if we actually have a CXX program

-if test "$ac_cv_prog_CXX" = "" -o ! -x "$ac_cv_prog_CXX"; then

+if test "$ac_cv_prog_CXX" = "" -o ! -x `which "$ac_cv_prog_CXX"`; then

     { echo "$as_me:$LINENO: WARNING: could not find C++ compiler $ac_cv_prog_CXX" >&5

 echo "$as_me: WARNING: could not find C++ compiler $ac_cv_prog_CXX" >&2;}

     enable_cxx=no