splat: splat() and load_splat() do not support mask vectors
load: Fix constness in several unused SSE-specific routines
load/store: Make the store/load API consistently accept void* pointers
load: detail::insn::i_load does not need to return anything

The return value is never used
store: Remove a block of dead code
load/store: Pass pointers as char* to the backend to avoid casts there
Remove QtCreator project files
Use CRTP in all construct-expression types to reduce duplication
Implement load() and load_u() using construct expressions

The new approach is much more convenient since there's no need to
specify the destination type. For example, the following just works:

int8_t* p = ...
int8<16> a = load(p);

float32<4> b = load_u(p);

This is API-breaking change.