Remove extern from function prototypes

Author: kezorm

api/itoa.h

@@ -26,12 +26,11 @@
 extern "C" {
 #endif
 
-extern char* itoa(int value, char *string, int radix);
-extern char* ltoa(long value, char *string, int radix);
-extern char* utoa(unsigned value, char *string, int radix);
-extern char* ultoa(unsigned long value, char *string, int radix);
+char* itoa(int value, char *string, int radix);
+char* ltoa(long value, char *string, int radix);
+char* utoa(unsigned value, char *string, int radix);
+char* ultoa(unsigned long value, char *string, int radix);
 
 #ifdef __cplusplus
 } // extern "C"
 #endif
-