Merge pull request #3 from michalfapso/master

* extract: do not try to optimize out move_l
Change the license to 2-clause BSD license

Note, that old versions of the library can still be used under the
Boost Software License, version 1.0.
extract: Fix implementation of extract_bits on NEON
Restructure NEON support

Currently NEON support is inconsistent. SIMDPP_USE_NEON corresponds to a
hypothetical architecture where both double and single precision
floating point arithmetic is done on a vector unit. Also,
SIMDPP_USE_NEON_VFP_DP has fewer features than SIMDPP_USE_NEON, which is
not intuitive.

This commit restructures the NEON support so that:
* SIMDPP_USE_NEON performs all floating-point computations on VFP
* SIMDPP_USE_NEON_FLT_SP performs single precision floating-point
computations on NEON.

Note, that currently NEON and VFP instructions are freely mixed, which
may lead to low performance.
convert: Do not use NEON for floating-point conversion operations

Floating-point conversion operations may be imprecise on NEON, thus
perform then on VFP when only USE_NEON is selected.
test: Fix formatting of binary numbers
Move the all handling of architecture-set specifics to simd.h
Add a macro that expands to stringified version of SIMDPP_ARCH_NAMESPACE
Use simd.h as the primary interface to the library
Convert tests to use simd.h plus architecture macros directly
test: Use the same .cc file for all architectures
Replace autotools-based build system with CMake
doc: Use the default Doxygen stylesheet
Put some documentation on the main page
Include correct headers on AVX and AVX2

This is a regression introduced by the following commit:
83d1b39a2f2c0089bd6e035728123174bf83bf1d
test: Do not set CMAKE_CXX_FLAGS; use set_target_properties() instead
perf: Reenable compilation of (naive) benchmark code
perf: Include simdpp/simd.h directly
Remove the old simdpp/simd.h wrappers
test: Improve inline documentation