Fix bugs in the PZX implementation

- PULS repetition count of zero (0x8000) is not allowed.
- Zero-length pulse at beginning of tape caused crash.
- Tidy messages.

Clarify tape code

Reimplement sound filters to use accumulators.

The previous implementation using buffers was very inefficient.
Thanks Patrik Rak for the comment and hint.

Fix sound stutter in Windows/MinGW builds

- Using SFML for timers/clocks instead of Boost/C   stdlib
- Removed Boost as dependency, as it is unused (except for tests)
- Fixed Z80FileTest compilation
- Removed Z80File unused member

Fix starting t-state when loading Z80 snaps

Cleanup ULA video signal generation

The new implementations uses the ULA fixed screen drawing order
to avoid using a bunch of if-else if-else constructions.

Solve clicks in Windows

Caused because sleep() needs more margin

Fix CMakeLists.txt for snap generation

Fixes

- Expected value for LD_BYTES trap.
- Fixes in CMakeLists.txt

Fix TZX Generalized Data Block implementation