Mention usage of :log in the DEBUG, LOG and WARNING macros'

documentation, and remove useless indications in ERROR's documentation
(the 'error' log level cannot be cancelled).

data/core/macros/interface-utils.cfg

@@ -446,7 +446,7 @@
 #define DEBUG TEXT
     # Logs a debug message to console. It does nothing unless the 'wml'
     # log domain is set to debug level at application startup (usually with
-    # --log-debug=wml).
+    # --log-debug=wml), or in-game with the :log command (e.g. :log debug wml).
     #
     # Example:
     # ! {DEBUG "inconsistency: $unit.id is not loyal!"}
@@ -459,7 +459,7 @@
 #define LOG TEXT
     # Logs a message to console. It does nothing unless the 'wml'
     # log domain is set to log level at application startup (usually with
-    # --log-info=wml).
+    # --log-info=wml), or in-game with the :log command (e.g. :log info wml).
     #
     # Example:
     # ! {LOG "player moved to forbidden location"}
@@ -472,7 +472,7 @@
 #define WARNING TEXT
     # Logs a warning to console. It does nothing unless the 'wml'
     # log domain is set to warning level at application startup (usually with
-    # --log-warning=wml).
+    # --log-warning=wml), or in-game with the :log command (e.g. :log warning wml).
     #
     # Example:
     # ! {WARNING "malformed unit data"}
@@ -483,9 +483,7 @@
 #enddef
 
 #define ERROR TEXT
-    # Logs an error to console. It does nothing unless the 'wml'
-    # log domain is set to error level at application startup (usually with
-    # --log-error=wml), which is the default.
+    # Logs an error to console.
     #
     # Example:
     # ! {ERROR "could not respawn hero at 2,4"}