Fix typo
Fix underestimation of buffer requirements with vertical WORD resizer
Make Filter destructor virtual
Cosmetics
Obtain M_PI by defining _USE_MATH_DEFINES
Add missing includes
Add missing "typename" keyword to dependent types
Reuse base class "what" function
Add crappy build system for Unix
Makefile: Install the headers
Add paramater --enable-x86simd (disabled by default)

And hopefully allow compiling for non-x86 systems.