Fix missing help pages resulting from non-well-formed markup.

Most of the special case asciidoc replacements were also removed since
they're a bit confusing and doing so results in a 60% improvement in the
time taken by asciidoc to process the help pages.  Unfortunately, I'm
now limited to preparing a three course menu for my guests while it runs
rather than the degustation extravaganzas of the past but such is life.

It's still a bit of a mess but since we're almost certainly moving to
something else in the near future it's probably not worth cleaning it up
before 2.0 is released.

vimperator/locale/en-US/options.txt

@@ -239,9 +239,9 @@ ____
 |\'ds'| |\'defsearch'|
 ||'defsearch' 'ds'|| string (default: "google")
 ____
-Sets the default search engine.
-The default search engine name is used in the [c]:[tab]open [arg][c] command if
-[[arg]] neither looks like a URL or like a specified search engine/keyword.
+Sets the default search engine. The default search engine name is used in the
+[c]:[tab]open [arg][c] command if [a][arg][a] neither looks like a URL or like
+a specified search engine/keyword.
 
 This means, it you set 'defsearch' to "youtube", then [c]:open arnold
 schwarzenegger[c] will be exactly the same as [c]:open youtube arnold
@@ -249,7 +249,7 @@ schwarzenegger[c]. Therefore, you need to add a keyword or search engine
 "youtube" first.
 
 If 'defsearch' is empty, then Firefox will always attempt to open the
-raw [[arg]].
+raw [a][arg][a].
 ____
 
 
@@ -528,7 +528,7 @@ ____
 ||'pageinfo' 'pa'||
 charlist (default: gfm)
 ____
-Desired info on [c]:pa[geinfo][c].  Available items:
+Desired info on [c]:pa[geinfo][c]. Available items:
 
 .--------`----------------
 *g*      General info