patch 7.4.1064
Problem:    When a spell file has single letter compounding creating
            suggestions takes an awful long time.
Solution:   Add th eNOCOMPOUNDSUGS flag.
diff --git a/runtime/doc/spell.txt b/runtime/doc/spell.txt
index 5a802a2..8ead3e6 100644
--- a/runtime/doc/spell.txt
+++ b/runtime/doc/spell.txt
@@ -1386,6 +1386,14 @@
 
 The Hunspell feature to use three arguments and flags is not supported.
 
+							*spell-NOCOMPOUNDSUGS*
+This item indicates that using compounding to make suggestions is not a good
+idea.  Use this when compounding is used with very short or one-character
+words.  E.g. to make numbers out of digits.  Without this flag creating
+suggestions would spend most time trying all kind of weird compound words.
+
+	NOCOMPOUNDSUGS ~
+
 							*spell-SYLLABLE*
 The SYLLABLE item defines characters or character sequences that are used to
 count the number of syllables in a word.  Example: