patch 8.1.0654: when deleting a line text property flags are not adjusted

Problem:    When deleting a line text property flags are not adjusted.
Solution:   Adjust text property flags in preceding and following lines.
diff --git a/src/misc2.c b/src/misc2.c
index 3834979..07bdf85 100644
--- a/src/misc2.c
+++ b/src/misc2.c
@@ -1351,6 +1351,20 @@
 }
 
 /*
+ * Copy "p[len]" into allocated memory, ignoring NUL characters.
+ * Returns NULL when out of memory.
+ */
+    char_u *
+vim_memsave(char_u *p, int len)
+{
+    char_u *ret = alloc((unsigned)len);
+
+    if (ret != NULL)
+	mch_memmove(ret, p, (size_t)len);
+    return ret;
+}
+
+/*
  * Same as vim_strsave(), but any characters found in esc_chars are preceded
  * by a backslash.
  */