Deprecate advanced streaming functions (#3408)

Deprecate advanced streaming functions (#3408)

* deprecate advanced streaming functions

* remove internal usage of the deprecated functions

* nit

* suppress warnings in tests/zstreamtest.c

* purge ZSTD_initDStream_usingDict

* nits

* c90 compat

* zstreamtest.c already disables deprecation warnings!

* fix initDStream() return value

* fix typo

* wasn't able to import private symbol properly, this commit works around that

* new strategy for zbuff

* undo zbuff deprecation warning changes

* move ZSTD_DISABLE_DEPRECATE_WARNINGS from .h to .c