new string.h implementation & tests

include/string.h

@@ -0,0 +1,10 @@
+#include <stdint.h>
+
+int memcmp(const void *s1, const void *s2, uint32_t n);
+void *memcpy(void *dest, const void *src, uint32_t n);
+void *memset(void *s, int c, uint32_t n);
+int strcmp(const char *s1, const char *s2);
+char *stpcpy(char *restrict dst, const char *restrict src);
+char *strcpy(char *restrict dst, const char *restrict src);
+uint32_t strlen(const char *s);
+char *strncpy(char *restrict dst, const char *restrict src, uint32_t dsize);