TDbf 6.3.6 released

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V6.3.6

- fixed: crash when optimizing expression with constants
- fixed: expression parser to use variable-length string variables for non-raw
fields
- added: support for opening (memory) streams as file
- fixed: numeric mdx compatibility bug; bytes instead of decimals (rep by rpoverdijk)
- fixed: integer fields store numerics padded with zeroes; now it uses spaces
- added: use new, faster assembler SwapInt64 from arioch