SLOG_SetPreviewName
Set the filename of the to be copied Preview file and Copy the file's content to the SLOG file 
Synopsis
int SLOG_SetPreviewName( SLOG_STREAM *slog, const char *pview_filename )
Unmodified Input parameter
- pview_filename  - pointer to the characters of the Preview's filename.
If no file is supplied, "/dev/null" should be
supplied to avoid checking of file SLOG_Preview.txt
in working directory.
Modified Input parameter 
- slog  - pointer to the SLOG_STREAM where interval records are stored.
Modified Output parameter 
- returned value  - integer return status code.
Include file need
slog_preview.h
Notes on SLOG return status code 
There are 5 allowed SLOG returned status codes.  They include
SLOG_SUCCESS, SLOG_FAIL and SLOG_EOF.  Their actual values
are defined in slog.h
SLOG_SUCCESS is returned when no error is encountered.
SLOG_FAIL is returned when error is encounted.
SLOG_EOF is returned when End of file is encounted.
There are also SLOG_TRUE and SLOG_FALSE which are sued as boolean
values, in particular they are used in boolean functions which
are usually named as IsXXXXX(), AreXXXXX() and HasXXXXX().
Location:../src/slog_preview.c