New user-friendly function to compare variables

Great commit. Everything looks nice. We should make a ticket though that at one point in time we should remove one of the two implementations .. 

Fix test

Minor

Unlikely to make any timing difference, but makes it slightly easier to read
the code.

Since the 'finally' block requires 'add_stack_trace_on_call' to be defined,
technically it is better to define it out of the 'try' block. Most likely
doesn't matter here though.

fix bug in equal_computation when comparing a variable with itself

Fixed test_linalg.py:test_spectral_radius_bound

Was broken by a6e1769d.
This fix also includes some coding style fixes.

Remove deprecated stuff

Make scan opt before blas opt.

Fix neibs

Spectral radius bound review

Depricated scan

They should not have been used anymore as they should have been removed already.

Was accepted only in theano.function in the mode argument. Not as a theano flags.