general: Miscellaneous documentation updates

- Add missing documentation for options and environment variables
- Rearrange definition and documentation of 'Options', 'Variables'
  and 'Aliases' in a consistent order

modules/environment/README.md

@@ -5,8 +5,38 @@ Sets general shell options and defines environment variables.
 
 This module must be loaded first.
 
-Environment Variables
----------------------
+Options
+-------
+
+### General
+
+  - `COMBINING_CHARS` combine zero-length punctuation characters (accents) with
+    the base character.
+  - `INTERACTIVE_COMMENTS` enable comments in interactive shell.
+  - `RC_QUOTES` allow 'Henry''s Garage' instead of 'Henry'\''s Garage'.
+  - `MAIL_WARNING` don't print a warning message if a mail file has been accessed.
+
+### Jobs
+
+  - `LONG_LIST_JOBS` list jobs in the long format by default.
+  - `AUTO_RESUME` attempt to resume existing job before creating a new process.
+  - `NOTIFY` report status of background jobs immediately.
+  - `BG_NICE` don't run all background jobs at a lower priority.
+  - `HUP` don't kill jobs on shell exit.
+  - `CHECK_JOBS` don't report on jobs when shell exit.
+
+Variables
+---------
+
+### Termcap
+
+  - `LESS_TERMCAP_mb` begins blinking.
+  - `LESS_TERMCAP_md` begins bold.
+  - `LESS_TERMCAP_me` ends mode.
+  - `LESS_TERMCAP_se` ends standout-mode.
+  - `LESS_TERMCAP_so` begins standout-mode.
+  - `LESS_TERMCAP_ue` ends underline.
+  - `LESS_TERMCAP_us` begins underline.
 
 Contributors
 ------------