Compress a string or screen image with RLE.
──────────────────────────────────────────────────────────────────────────────

 Syntax

        GT_RleComp(<cString>,[<lIsAScreen>]) --> cCompressed

 Arguments:

      <cString> is the string to be compressed.

      <lIsAScreen> is an optional logical paramepet to tell the
      function that the string is a screen image. The default value
      is TRUE.

 Returns:

      A Compressed version of the string or screen image.

 Description:

      GT_RleComp() uses a form of run length encoding to compress a
      string, This form of compression is only any good on strings
      that have a lot of repeating characters.

      By default GT_RleComp() is optimized to compress screen images
      as returned by Clipper's SaveScreen() function. When compressing
      ``normal'' strings this optimisation will not work so you must
      tell the function to use the ``normal'' compression method.

 Examples:


      // Save the screen and compress it.

      cScreen := GT_RleComp(savescreen())
      ...
      restscreen(0,0,maxrow(),maxcol(),GT_RleUnCo(cScreen))

      // Compress a normal string and print it's length.

      cString := space(1000)
      ? len(GT_RleComp(cString,.F.))

 Source: RLE.C

 Author:  Dave Pearson