Update healpix-cxx to 3.60

[lpsinger]

Fixes #576.

This should work but for the two issues mentioned in #576 that must first be fixed in the HEALPix svn repository.

[lpsinger]

@mreineck, the build is failing with this error message:

In file included from healpy/src/_sphtools.cpp:635:0:
1675/home/travis/build/healpy/healpy/build/temp.linux-x86_64-2.7/include/healpix_cxx/weight_utils.h:71:10: error: ‘unique_ptr’ in namespace ‘std’ does not name a template type
1676     std::unique_ptr<weight_utils_detail::FullWeightImpl> impl;
1677          ^
1678

Do we need to build with -std=c++11?

[mreineck]

Do we need to build with -std=c++11?

Yes, that will be necessary.

[lpsinger]

@zonca, the build is now passing. This is ready for review.

[zonca]

thanks @lpsinger for making this work!