1. Write the strchr() function.
2. Write a function that returns the number of occurrences of a given character within a given C-string.
3. Write and test the strrchr() function.
4. Write and test the strstr() function.
5. Write and test the strncpy() function.
6. Write and test the strcat() function.
7. Write and test the strcmp() function.
8. Write and test the strncmp() function.
9. Write and test the strspn() function.
10. Write and test the strcspn() function.
11. Write and test the strpbrk() function.