added experimental code to call function held in a variable

qse/doc/page/awk-lang.md

@@ -598,12 +598,27 @@ can't confict with named variables and globals variables.
  Built-in Functions
 -------------------------
 
+- close
+- fflush
+- int
+- typename
+- isnil
 - index
 - length
+- substr
+- split
+- tolower
+- toupper
+- gsub
+- sub
+- match
+- sprintf
+- mktime
+- strftime
+- systime
 
 TBD.
 
-
  Function Calls
 -----------------------