patch 8.0.1357: startup test fails on OpenBSD

Problem:    Startup test fails on OpenBSD. (Edd Barrett)
Solution:   Check for "BSD" instead of "FreeBSD" being defined. (James McCoy,
            closes #2376, closes #2378)
diff --git a/src/vim.h b/src/vim.h
index 1c2b795..bf6c3d3 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2485,7 +2485,8 @@
 #define FNE_INCL_BR	1	/* include [] in name */
 #define FNE_CHECK_START	2	/* check name starts with valid character */
 
-#if (defined(SUN_SYSTEM) || defined(__FreeBSD__) || defined(__FreeBSD_kernel__)) \
+/* BSD is supposed to cover FreeBSD and similar systems. */
+#if (defined(SUN_SYSTEM) || defined(BSD) || defined(__FreeBSD_kernel__)) \
 	&& defined(S_ISCHR)
 # define OPEN_CHR_FILES
 #endif