patch 8.0.0914: highlight attributes are always combined
Problem: Highlight attributes are always combined.
Solution: Add the 'nocombine' value to replace attributes instead of
combining them. (scauligi, closes #1963)
diff --git a/runtime/doc/syntax.txt b/runtime/doc/syntax.txt
index 9bf3888..dda2e66 100644
--- a/runtime/doc/syntax.txt
+++ b/runtime/doc/syntax.txt
@@ -4689,6 +4689,7 @@
*bold* *underline* *undercurl*
*inverse* *italic* *standout*
+ *nocombine*
term={attr-list} *attr-list* *highlight-term* *E418*
attr-list is a comma separated list (without spaces) of the
following items (in any order):
@@ -4699,6 +4700,7 @@
inverse same as reverse
italic
standout
+ nocombine override attributes instead of combining them
NONE no attributes used (used to reset it)
Note that "bold" can be used here and by using a bold font. They