Document new predicates.

doc/mbase.md

@@ -216,6 +216,34 @@ periods.
 Returns ```#t``` if given member exists - that is the current month is
 within any of the member (membership) periods.
 
+    (brmember-chair? mr)
+
+* ```mr``` - a member record structure
+
+Returns ```#t``` if given ```mr``` is chair as of
+```(*current-day*)```.
+
+    (brmember-council? mr)
+
+* ```mr``` - a member record structure
+
+Returns ```#t``` if given ```mr``` is a member of council as of
+```(*current-day*)```.
+
+    (brmember-revision? mr)
+
+* ```mr``` - a member record structure
+
+Returns ```#t``` if given ```mr``` is a member of revision committee
+as of ```(*current-day*)```.
+
+    (brmember-grant? mr)
+
+* ```mr``` - a member record structure
+
+Returns ```#t``` if given ```mr``` is a member of grant committee as
+of ```(*current-day*)```.
+
     (brmember-flags mr)
 
 * ```mr``` - a member record structure
@@ -227,6 +255,10 @@ Returns a list of member flags which can be any of the following:
 * ```'active```
 * ```'destroyed```
 * ```'existing```
+* ```'chair```
+* ```'council```
+* ```'revision```
+* ```'grant```
 
 The ```'existing``` and ```'destroyed``` are mutually exclusive. Also
 ```'active``` and ```'suspended``` are mutually exclusive.