patch 8.2.1818: SE Linux: deprecation warning for security_context_t

Problem:    SE Linux: deprecation warning for security_context_t.
Solution:   Use "char *" instead. (James McCoy, closes #7093)
diff --git a/src/os_unix.c b/src/os_unix.c
index 2afe1ba..40df6b7 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -2832,8 +2832,10 @@
 
     if (selinux_enabled > 0)
     {
-	security_context_t from_context = NULL;
-	security_context_t to_context = NULL;
+	// Use "char *" instead of "security_context_t" to avoid a deprecation
+	// warning.
+	char *from_context = NULL;
+	char *to_context = NULL;
 
 	if (getfilecon((char *)from_file, &from_context) < 0)
 	{