Docs and so forth for macro-string/compileMacro changes that snuck into a previous commit.

common/content/io.js

@@ -639,7 +639,7 @@ execute 'syn match <name>Option "\<\%(no\|inv\)\=\%(' .
     \ join(s:toggleOptions, '\|') .
     \ '\)\>!\=" contained nextgroup=<name>SetMod'
 
-syn match <name>SetMod "\%(\<lt>[a-z_]\+\)\@<=&" contained
+syn match <name>SetMod "\%(\<[a-z_]\+\)\@<=&" contained
 
 syn region <name>JavaScript start="\%(^\s*\%(javascript\|js\)\s\+\)\@<=" end="$" contains=@javascriptTop keepend oneline
 syn region <name>JavaScript matchgroup=<name>JavaScriptDelimiter
@@ -650,7 +650,7 @@ execute 'syn region <name>Css start="' . s:cssRegionStart . '" end="$" contains=
 execute 'syn region <name>Css matchgroup=<name>CssDelimiter'
     \ 'start="' . s:cssRegionStart . '<<\s*\z(\h\w*\)"hs=s+2 end="^\z1$" contains=@cssTop fold'
 
-syn match <name>Notation "<lt>[0-9A-Za-z-]\+>"
+syn match <name>Notation "<[0-9A-Za-z-]\+>"
 
 syn match   <name>Comment +".*$+ contains=<name>Todo,@Spell
 syn keyword <name>Todo FIXME NOTE TODO XXX contained

common/locale/en-US/options.xml

@@ -93,19 +93,20 @@
     the form of <em>&lt;<a>name</a>></em>. These tokens are replaced by
     the parameter <a>name</a> as specified in the relevant documentation.
     If the token is in the form <em>&lt;q-<a>name</a>></em>, the value of the
-    parameter is automatically <link topic="quoting">quoted</link>.
+    parameter is automatically <link topic="quoting">quoted</link>. If it is in
+    the form of <em>&lt;e-<a>name</a>></em>, its value is never shown but may be
+    used to test whether the given parameter is empty.
 </p>
 <p>
-    Any substring enclosed by <em>&lt;[</em>
-    and <em>]></em> is automatically elided if any of the contained macros
-    characters aren't currently valid. A literal <em>&lt;</em> or <em>></em>
-    character may be included with the special escape sequences <em>&lt;lt></em>
-    or <em>&lt;gt></em> respectively.
+    Any substring enclosed by <em>&lt;{</em> and <em>}></em> is automatically
+    elided if any of the contained macros characters aren't currently valid. A
+    literal <em>&lt;</em> or <em>></em> character may be included with the
+    special escape sequences <em>&lt;lt></em> or <em>&lt;gt></em> respectively.
 </p>
 
 <p>
     For example, given the format string
-    <str><em>&lt;[</em>(cmd: <em>&lt;column></em>) <em>]>&lt;[</em>line: <em>&lt;line> ]>&lt;file></em></str>,
+    <str><em>&lt;{</em>(cmd: <em>&lt;column></em>) <em>}>&lt;{</em>line: <em>&lt;line> }>&lt;file></em></str>,
     where <em>line</em>=<hl key="Number">32</hl> and
     <em>file</em>=<str delim="'">Lieder eines fahrenden Gesellen.txt</str>,
     the result is formatted as

common/modules/util.jsm

@@ -303,9 +303,9 @@ var Util = Module("Util", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
         let re = util.regexp(<![CDATA[
             ([^]*?) // 1
             (?:
-                (<\[) | // 2
+                (<\{) | // 2
                 (< ((?:[a-z]-)?[a-z-]*?) >) | // 3 4
-                (\]>) // 5
+                (\}>) // 5
             )
         ]]>, "giy");
         while (match = re.exec(macro)) {
@@ -348,7 +348,7 @@ var Util = Module("Util", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
         if (end < macro.length)
             stack.top.elements.push(macro.substr(end));
 
-        util.assert(stack.length === 1, "Unmatched <[ in macro");
+        util.assert(stack.length === 1, "Unmatched <{ in macro");
         return stack.top;
     },