Fix a crash on Mac OS when sys.prefix is different from its realpath

The problem was that new_path was actually in the environment variable,
but when realpath(v) was called, it became a different string (starting
with a single backslash instead of two).
Merge pull request #1463 from lamblin/fix_macos_path_check

Fix a crash on Mac OS when sys.prefix is different from its realpath
Merge pull request #1464 from delallea/minor

Minor fixes
Fix a test in float32.
Fix error reporting when the error is reported by the input, not by an op.
Safer indexing. If we append more information, it will work correctly.
Fix a test error related type typenum of ulonglong and uint64 being different even if they are equivalent.
Fix theano.grad() verification of compute_test_value for op with multiple outputs.
Fix compute_test_value with DisconnectedType grandient.
add debug info
remove not used import
remove deprecation warning in tests.
remove var not used and not needed in test.
pep8
Merge pull request #1465 from nouiz/tests

Tests
fix gh-1461
pep8
Add comment to tell to don't use the old neighbourhoods.py version and point to the new ones.

Also make sure the input is on the CPU, so a transfer is added when needed.
Implement GpuImages2Neibs mode ignore_border.
Don't try to move to the GPU alloc that aren't float32.

This is needed to make the new GpuImages2Neibs ignore_border mode pass.