Add rstrlcpy() string helper function

- adopted from strlcpy() function of OpenBSD originally developed by
  Todd C. Miller <Todd.Miller@courtesan.com>

rpmio/rpmstring.c

@@ -288,3 +288,31 @@ char *rstrscat(char **dest, const char *arg, ...)
     return dst;
 }
 
+/*
+ * Adapted from OpenBSD, strlcpy() originally developed by
+ * Todd C. Miller <Todd.Miller@courtesan.com>
+ */
+size_t rstrlcpy(char *dest, const char *src, size_t n)
+{
+    char *d = dest;
+    const char *s = src;
+    size_t len = n;
+
+    /* Copy as many bytes as will fit */
+    if (len != 0) {
+	while (--len != 0) {
+	    if ((*d++ = *s++) == '\0')
+		break;
+	}
+    }
+
+    /* Not enough room in dst, add NUL and traverse rest of src */
+    if (len == 0) {
+	if (n != 0)
+	    *d = '\0'; /* NUL-terminate dst */
+	while (*s++)
+	    ;
+    }
+
+    return s - src - 1; /* count does not include NUL */
+}

rpmio/rpmstring.h

@@ -124,6 +124,18 @@ char *rstrcat(char **dest, const char *src);
  */
 char *rstrscat(char **dest, const char *arg, ...) RPM_GNUC_NULL_TERMINATED;
 
+/** \ingroup rpmstring
+ * strlcpy() clone: 
+ * Copy src to string dest of size n. At most n-1 characters
+ * will be copied.  Always zero-terminates (unless n == 0).
+ * Length of src is returned; if retval >= n, truncation occurred.
+ * @param dest		destination buffer
+ * @param src		string to copy
+ * @param n		destination buffer size
+ * @return		length of src string
+ */
+size_t rstrlcpy(char *dest, const char *src, size_t n);
+
 /** \ingroup rpmstring
  * Split string into fields separated by a character.
  * @param str		string