This reverts commit 6d751c93bf.

Fixes https://github.com/nvaccess/nvda/issues/8231.

Valgrind reports

==20307== Invalid write of size 1
==20307==    at 0x4E856FE: Wavegen.part.1 (wavegen.c:880)
==20307==    by 0x4E86682: Wavegen (wavegen.c:670)
==20307==    by 0x4E86682: Wavegen2 (wavegen.c:1235)
==20307==    by 0x4E86682: WavegenFill2 (wavegen.c:1317)
==20307==    by 0x4E86CA7: WavegenFill (wavegen.c:1398)
==20307==    by 0x4E7093F: Synthesize (speech.c:442)
==20307==    by 0x4E712E0: sync_espeak_Synth (speech.c:549)
==20307==    by 0x4E8A5C0: process_espeak_command (espeak_command.c:317)
==20307==    by 0x4E8B387: say_thread (fifo.c:333)
==20307==    by 0x50E85A9: start_thread (pthread_create.c:463)
==20307==    by 0x53F5CBE: clone (clone.S:95)
==20307==  Address 0xad5e1bd is 0 bytes after a block of size 2,205 alloc'd
==20307==    at 0x4C2CABF: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==20307==    by 0x4C2EE04: realloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==20307==    by 0x4E70CFC: espeak_ng_InitializeOutput (speech.c:286)
==20307==    by 0x4E6176E: espeak_Initialize (espeak_api.c:67)
==20307==    by 0x10A5D8: initialize_espeak (espeak.c:303)
==20307==    by 0x109D1D: main (espeakup.c:201)
==20307==

Indeed, the out_ptr >= out_end test is not enough: it only checks that
one byte can fit the buffer, while klatt and wavegen produce two bytes.

This makes the codebase more consistent. Including speech.h is not necessary anymore in some files. Includes have been removed.

See issue #8, https://github.com/espeak-ng/espeak-ng/issues/8

There might still be some ints that could be changed to boolean.

Possible regressions in fifo.c:
int fifo_is_busy() and int fifo_is_command_enabled() used to return an int. Now they return a boolean. This might cause problems on systems where stdbool true/false is something else than 1/0.

Moved include/espeak/speak_lib.h to include/espeak-ng/speak_lib.h and
created a symlink from the original location.

This can occur in cases where the voice is not found, or
espeak_ng_Initialize is called more than once.

This commit has been reported to cause distortions in phoneme
pitches and speeds.

This is from the old espeak RiscOS port that has been removed.

If/when the espeak-ng program is ported to RiscOS, this will be
done in a different, more maintainable way.

Also use size_t instead of int in some places
where it make sense

This allows newer versions of sonic to be used and to keep
up-to-date with bug fixes provided by the system.