feat: added memchr, memcmp, memmv and realloc

srcs/ft_memcmp.c

@@ -0,0 +1,28 @@
+#include <stddef.h>
+#include <stdint.h>
+
+int ft_memcmp(const void *s1, const void *s2, size_t n)
+{
+    const unsigned char *p1 = s1, *p2 = s2;
+
+    while (n >= sizeof(size_t)) {
+        size_t w1 = *(const size_t *)p1;
+        size_t w2 = *(const size_t *)p2;
+        if (w1 != w2) {
+            for (size_t i = 0; i < sizeof(size_t); ++i) {
+                if (p1[i] != p2[i])
+                    return (p1[i] - p2[i]);
+            }
+        }
+        p1 += sizeof(size_t);
+        p2 += sizeof(size_t);
+        n  -= sizeof(size_t);
+    }
+    while (n--) {
+        if (*p1 != *p2)
+            return (*p1 - *p2);
+        ++p1;
+        ++p2;
+    }
+    return (0);
+}