Fix S3M shared memory for all affected effects

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
[test] Add OpenMPT S3M ParamMemory test case

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Fix envelope position effect

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>