Implemented implicit reference-style links to section headers in markdown.

For example, if you have a header '# Supported architectures', you can
link to it with '[Supported architectures]'.  If there are multiple
headers with this label, the link will point to the first of them.
Implicit references are always overridden by explicitly specified references.
Addresses Issue #20.

+ Moved isPunctuation, uniqueIdentifiers, and inlineListToIdentifier from
  Text.Pandoc.Writers.HTML to Text.Pandoc.Shared.

+ Added stHeaders to ParserState.   This holds a list of header texts
  used in the document, and is used to construct implicit header references.

+ In Text.Pandoc.Readers.Markdown, added call to headerReference
  parser in initial parsing pass, constructing a list of section header
  labels. This is then passed to uniqueIdentifiers to produce
  identifiers, and a list of implicit references is constructed. This is
  added to the end of the explicitly specified references, so it will be
  overridden by explicitly specified references. All of this processing
  is skipped if --strict was specified.

+ Modified documentation in README.



git-svn-id: https://pandoc.googlecode.com/svn/trunk@1086 788f1e2b-df1e-0410-8736-df70ead52e1b

1 files changed, 23 insertions, 3 deletions

diff --git a/README b/README
index a4085db5e..f1361fcd7 100644
--- a/README
+++ b/README
@@ -299,7 +299,7 @@ For further documentation, see the `pandoc(1)` man page.
 :   includes *string* as a prefix at the beginning of the title that
     appears in the HTML header (but not in the title as it appears at
     the beginning of the HTML body). (See below on
-    [Title Blocks](#title-blocks).)
+    [Title Blocks].)
 
 `-S` or `--smart`
 :   causes `pandoc` to produce typographically correct output, along the
@@ -797,8 +797,28 @@ another. A link to this section, for example, might look like this:
 
     See the section on [header identifiers](#header-identifiers-in-html). 
 
-Note, however, that this method of providing links to sections works
-only in HTML.
+Note that this method of providing links to sections works only in
+HTML.
+
+Shortcut links to section headers
+---------------------------------
+
+You may use the following shortcut to link to a section header:
+
+    See the section on [Header identifiers in HTML].
+
+Pandoc will behave as if the document contains
+
+    [Header identifiers in HTML]: #header-identifiers-in-html
+
+If there are multiple headers labeled "Header identifiers in HTML",
+this will link to the first one. Note that implicit references are always
+overridden by explicit ones, so the link in the following text
+will be to `/url`, not `#header-identifiers-in-html`:
+
+    See the section on [Header identifiers in HTML].
+
+    [Header identifiers in HTML]: /url
 
 Box-style blockquotes
 ---------------------