Moved compression/decompression routines to separate file

Samo Penic

2019-10-19 dba66b4f8a25cb7eb18de5f7ffca97e179d7a5d9

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Original written by Dan Kroll in FORTRAN. Code was then largely adapted and commented by Miha Fosnaric-Fosni. Rewritten into C by Samo Penic-Peni, with help of Miha's extensive explanations.