Count the occurrences of a character in a string.
returnedNum = strchrcount(string, characterString)
returnedNum - type: num
string - type: str
characterString - type: str
The number of times char occurs in string.
characterString must consist of a single character.
G("count") = strchrcount("abcabc","b");
# This should evaluate to 2, for the two occurrences of "b" in "abcabc".