gunzip a file
    
    gunzip(filename, destname = gsub("[.]gz$", "", filename), overwrite = FALSE, remove = TRUE, BFR.SIZE = 1e+07)
    
    Arguments
    
      - filename
- The filename to be unzipped
- destname
- The destination file
- overwrite
- Boolean indicating whether or not to overwrite a
    destfile of the same name
- remove
- Boolean indicating whether or not to remove the original
  file after completion
- BFR.SIZE
- The size of the read buffer....
      Details
      This function was stripped out of R.utils due to breaking some stuff
  on the bioconductor build machine.
     
    
      Value
      Invisibly, the number of bytes read.