Changed indices in openmp loops to signed types

This is a requirement of OpenMP 2.5 specification
Win32 build
Merge commit '8781c10ac75bc2c89cf7bb25a39269568969af4b'
Scaled additive transforms

c * (A * x); c * (X * S); c * S_op(X);
where c is a scalar value, A is a matrix, S is a stencil,
and S_op is stencil operator.
utest for vector types arithmetic
Signed/unsigned mismatch continued
Unused parameters
Missing braces in initialization
Again, signed/unsigned mismatch

MS Visual Studio only supports OpenMP v2.5, and that requires signed
index types in parallel for loops
see: http://www.bealto.com/gpu-fft2.html
from 2011-12-11 tarball. Public Domain.
Changed the way additive transforms are applied internally

Use boost::proto::flatten to get a sequence of (possibly negated) additive
transforms. Head of the sequence possibly needs initialization, and tail of the
sequence is always appended to the result.

@neapel now both negate and append are truly compile time constants, so it
should be possible to use static asserts with types that do not support
appending or negation.
New year in copyright clause
Touched license file
Add argument for build option string
Add type traits to convert between vector versions of CL types.
Alternative OpenCL FFT implementation.
Based on Eric Bainville's, but replaces hard-coded kernels with a generator function to create arbitrary power-of-2 radixes (which should make it easier to add non-power-of-2s).
Supports n-dimensional transforms using transposition kernel based on NVIDIA sample.
FFT tests: verify against FFTw, benchmark against CuFFT
Merge branch 'master' of https://github.com/ddemidov/vexcl

Conflicts:
	examples/CMakeLists.txt
Merge branch 'fft'
link Boost to FFT examples, too