;doc: orgfiles: disable smart dashes in another way

Use an org export setting in BACKLOG.org and ROADMAP.org to disable
-- being converted to dashes. Leave the markdown+smart workaround
in Shake.hs also, it's doing no harm and seems useful as backup.

':nil would disable smart quotes as well, but that seems to be org's
default.

BACKLOG.org

@@ -1,5 +1,5 @@
 * BACKLOG.org
-#+OPTIONS: H:2
+#+OPTIONS: H:2 -:nil
 
 An efficient public store of tasks/changes/design notes, mostly from
 SM's private backlog; things that I/we feel would be nice to have, or

ROADMAP.org

@@ -1,4 +1,5 @@
 * ROADMAP.org
+#+OPTIONS: -:nil
 
 Ideas about where the hledger project should be going next. Being
 listed here suggests a bit of commitment, perhaps even a schedule.

Shake.hs

@@ -124,8 +124,9 @@ grep = "grep -E"
 fromsrcmd = "-f markdown-smart-tex_math_dollars"
 
 -- The kind of org markup used in any org source files.
--- As of pandoc 2.14, org reader always enables smart and -smart has no effect here
--- (but writing to markdown+strict will help, undoing the smart typography).
+-- In pandoc 2.14, org reader enables smart dashes by default;
+-- use #+OPTIONS: -:nil in the org file to disable it (-smart here has no effect).
+-- We also write to markdown+strict, which would undo any smart dashes or quotes).
 fromorg = "-f org-smart"
 
 -- The kind of markdown we like to generate for the website.
@@ -135,9 +136,10 @@ fromorg = "-f org-smart"
 --
 -- --markdown-headings=atx requires pandoc 2.11.2+; with older pandoc use --atx-headers instead.
 --
--- +smart here because "If you are writing Markdown, then the smart extension has the 
+-- In pandoc 2.14, "If you are writing Markdown, then the smart extension has the 
 -- reverse effect: what would have been curly quotes comes out straight.".
--- This fixes the unwanted smart typography in org docs (see above).
+-- So +smart here can fix unwanted smart typography that may have crept in,
+-- eg from org docs (see above).
 --
 towebmd = "-t markdown+smart-fenced_divs-fenced_code_attributes-simple_tables-multiline_tables-grid_tables-raw_attribute --markdown-headings=atx"