Count the number of times a substring appears in a string
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 Syntax

        GT_StrCount(<cChrs>, <cStr>) --> nFreq

 Arguments:

      <cChrs> - The substring to find the frequence of
      <cStr>  - The string in which to find the character

 Returns:

      nFreq   - The number of times <cChrs> occurs in <cStr>

 Description:

      GT_StrCount() counts how many times a specified substring
      appears in a string.
      If the substring does NOT appear in <cStr> this function
      will return 0.
      If the substring is a single character use GT_ChrCount() as
      it will be faster.

      NOTE:
         invalid parameters will return -1

 Examples:


      ? GT_StrCount("the", "the cat sat on the mat")      // prints 2


 Source: STRCOUNT.C

 Author:  Andy M Leighton