Refactor string functions, add unicode support

Refactored existing functions. Added Unicode support and UTF-8, UTF-16,
and UTF-32 encoding/decoding.

src/String/Inline/Signed.h

@@ -0,0 +1,37 @@
+char tmp[sizeof(value) * CHAR_BIT + 2];
+char *current, *end;
+int sign;
+
+end = tmp + sizeof(tmp);
+current = end;
+sign = 0;
+
+/* Check for sign */
+if (value < 0)
+{
+    sign = 1;
+    value = -value;
+}
+
+/* Fill buffer from the end */
+*(--current) = 0;
+while (value)
+{
+    *(--current) = digits[value % base];
+    value /= base;
+}
+
+/* Append sign */
+if (sign)
+    *(--current) = '-';
+
+/* Check that string have space for the result */
+if (size < (size_t)(end - current))
+    return BH_ERROR;
+
+/* Copy data */
+memcpy(string, current, end - current);
+if (actual)
+    *actual = end - current;
+
+return BH_OK;