Fix a warning for {snappy,lz4}-free compilation

Warning: "unused variable 'sbuffer'"

Other possible approaches include:

- `char sbuffer[256] __attribute__ ((unused));`

- `sbuffer[0] = 0; // to avoid an unused variable warning`

- refactoring to have `*version = strdup(...)` inside each case's block
Merge pull request #60 from andrewschaaf/unused-variable

Fix an unused variable warning for {snappy,lz4}-free compilation