new functions added

//friend function
friend long __dystrlen(const char *);  //find length of the string.

//operator overloading
dystring operator +(const char *str); //concatenate strings with string
constant. Example: str + "hello"
dystring operator +(dystring); //concatenate two strings. Example: str1
+ str2
friend dystring operator +(const char *str, dystring); //concatenate
string constant with string. Example: "hello" + str
long countChar(const char ch); //return the number of time character ch
occurs in the string.
long countConsonant(void);  //return the number of consonant in the
string.
long countConsonantLowerCase(void);  //return the number of lower case
consonant in the string.
long countConsonantUpperCase(void);  //return the number of upper case
consonant in the string.
long countVowel(void);  //return the number of vowels in the string.
long countVowelLowerCase(void);  //return the number of lower case
vowels in the string.
long countVowelUpperCase(void);  //return the number of upper case
vowels in the string.