Fix typo

Author: kimwalisch

doc/CPP_API.md

@@ -179,7 +179,7 @@ int main()
 
 Before using ```primesieve::iterator::prev_prime()``` you must change the start number
 either in the constructor or using the ```jump_to()``` method (because the start number is
-initialized to 0 be default).
+initialized to 0 by default).
 
 * Please note that the first ```prev_prime()``` invocation returns the first prime ≤ start number.
   If want to generate primes < start number you need to use e.g. ```jump_to(start-1)```.

doc/C_API.md

@@ -162,7 +162,7 @@ int main(void)
 ## ```primesieve_prev_prime()```
 
 Before using ```primesieve_prev_prime()``` you must first change the start number using the
-```primesieve_jump_to()``` function (because the start number is initialized to 0 be default).
+```primesieve_jump_to()``` function (because the start number is initialized to 0 by default).
 
 * Please note that the first ```primesieve_prev_prime()``` call returns the first prime ≤ start
   number. If want to generate primes < start number you need to use e.g. ```primesieve_jump_to(iter, start-1, stop)```.