Get a specific length string from memory.
------------------------------------------------------------------------------

 Syntax

        GT_PeekStN(<nSegment>,<nOffset>,<nLength>) --> cString

 Arguments:

      <nSegment> is the segment of the string in memory.

      <nOffset>  is the offset of the string in memory.

      <nLength>  is the length of the string.

 Returns:

      The string found at <nSegment>:<nOffset>.

 Description:

      GT_PeekStN() can be used for getting strings from specific areas
      of memory that are not NULL terminated.

 Examples:

      // Print the ROM BIOS date.

      ? GT_PeekStN(61440,65525,8)

 Source: PEEKSTRN.C

 Author:  David Pearson