boost: fixing boost-1.55.0 for gcc-5 (#2822)

boost-1.55.0 requires patching when compiling with gcc-5. See these
threads:

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=197594
https://svn.boost.org/trac/boost/ticket/10125

Fixes #2821.

var/spack/repos/builtin/packages/boost/package.py

@@ -130,6 +130,9 @@ class Boost(Package):
     # Patch fix from https://svn.boost.org/trac/boost/ticket/11856
     patch('boost_11856.patch', when='@1.60.0%gcc@4.4.7')
 
+    # Patch fix from https://svn.boost.org/trac/boost/ticket/10125
+    patch('boost_10125.patch', when='@1.55.0%gcc@5.0:5.9')
+
     def url_for_version(self, version):
         """
         Handle Boost's weird URLs,