SCP: Add'l memory sanitization fixes

Initialize de-dup'ed debug line buffer:

  realloc(NULL, size) == malloc(size), which results in an uninitialized
  debug line buffer and will fail memory sanitizer checks. Ensure that
  the buffers are memset() to zero when initially allocated.

Another Random Act of Memory (Sanitization):

  Clang's memory sanitizer found an off-by-one bug in sim_addr_acl_check
  while executing "testlib". This makes CIDR network ACLs functional,
  e.g., "127.0.0.1/32" is interpreted properly and the associated
  "testlib" test passes.

scp.c

@@ -13622,9 +13622,18 @@ if (sim_deb_switches & SWMASK ('F')) {              /* filtering disabled? */
     }
 AIO_LOCK;
 if (debug_line_offset + len + 1 > debug_line_bufsize) {
+    /* realloc(NULL, size) == malloc(size). Really. It is. Initialize
+     * the malloc()-ed space. */
+    int do_init = (NULL == debug_line_buf) || (NULL == debug_line_buf_last);
+
     debug_line_bufsize += MAX(1024, debug_line_offset + len + 1);
     debug_line_buf = (char *)realloc (debug_line_buf, debug_line_bufsize);
     debug_line_buf_last = (char *)realloc (debug_line_buf_last, debug_line_bufsize);
+
+    if (do_init) {
+        memset(debug_line_buf, 0, debug_line_bufsize);
+        memset(debug_line_buf_last, 0, debug_line_bufsize);
+        }
     }
 memcpy (&debug_line_buf[debug_line_offset], buf, len);
 debug_line_buf[debug_line_offset + len] = '\0';

sim_sock.c

@@ -721,7 +721,7 @@ if (c != NULL) {
     if ((c - validate_addr) > sizeof (v_cpy) - 1)
         return status;
     memcpy (v_cpy, validate_addr, c - validate_addr);   /* Copy everything before the / */
-    v_cpy[1 + c - validate_addr] = '\0';                /* NUL terminate the result */
+    v_cpy[c - validate_addr] = '\0';                    /* NUL terminate the result */
     validate_addr = v_cpy;                              /* Use the original string minus the prefix specifier */
     }
 if (p_getaddrinfo(validate_addr, NULL, NULL, &ai_validate))