[util][math] add sqrt function in bg::math namespace; this function
calls std::sqrt for fundamental number types and ::sqrt for everything
else; it helps avoiding implicit conversions for fundamental number
types when ::sqrt is called (in particular, we avoid the conversion
from long double to double when ::sqrt is called);
[util][math] update copyright header
[strategies] replace calls to ::sqrt by calls to bg::math::sqrt
[strategies] fix unused typedef warningy
[algorithms][equals] fix copyright years; replace call to ::sqrt
by call to bg::math::sqrt
[extensions] replace calls to ::sqrt by calls to bg::math::sqrt;
change has not been applied to projections and ttmath;
[extensions][algorithms][offset] remove obsolete include (file no
longer exists)
[util][math] fix return type of sqrt for fundamental number types
Merge branch 'develop' of https://github.com/boostorg/geometry into feature/math-sqrt
Merge branch 'feature/math-sqrt' of github.com:mkaravel/geometry into feature/math-sqrt
[util][math] fix return type for math::sqrt; fix implementation
for sqrt for non-fundamental types (use the using mechanism);
[test][util] add unit test for math::sqrt
[algorithms][io][test] Fix some rather harmless conversions warnings and add /bigobj for some tests for VS.
[extensions][test][projections] Fix compilation error in projections test.
[extensions][nsphere][test] Remove unused typedefs. Rename tests.
[test] Remove the #includes of geometry.hpp and multi/* from the relops tests
[buffer] Move from extensions to algorithms/detail
[buffer] update include guards/copyright info
[buffer] Changes in (folder)locations of strategies, and
moved buffer_side_selector and piece_type used by strategies.
Merge branch 'develop' of https://github.com/boostorg/geometry into feature/math-sqrt

Conflicts:
	include/boost/geometry/algorithms/detail/buffer/buffer_inserter.hpp