Code refactor, external xxHash

• Use FALL_THROUGH macro for falling through between switch cases.
• Allow use of external xxHash.
• MSVC cmake tweaks.

Improve unit tests

• Add new test case for a fixed crash.
• Fix dyn_table_cap_mismatch test case.

Fix crash qenc_remove_from_risked_list

• Fix corner case when qpe_risked_hinfos is empty.
• Allow headers total size >64KB.

Fix compiler warnings

• Fix compiler warnings #47

Fix compiler warnings

• Fix compiler warnings #46

Fix decoder dynamic table size change

[BUGFIX] Properly handle dynamic table size change at the beginning of decoding stream.

Fix use-after-free bug

• Fix use-after-free bug in handling decompression errors. (#43)

Fix crash when dynamic table size is too small

• Disable dynamic table when max_table_size < 32.

Better Windows support

Better packaging for Windows platform.

Bug fix to avoid assert() for input data error.

Replace assert() with RETURN_ERROR() for possible input data error.