Update spec.

Author: jgm

test/spec.txt

@@ -1,8 +1,8 @@
 ---
 title: CommonMark Spec
 author: John MacFarlane
-version: 0.28
-date: '2017-08-01'
+version: 0.29
+date: '2019-04-06'
 license: '[CC-BY-SA 4.0](http://creativecommons.org/licenses/by-sa/4.0/)'
 ...
 
@@ -827,7 +827,7 @@ Contents are parsed as inlines:
 ````````````````````````````````
 
 
-Leading and trailing blanks are ignored in parsing inline content:
+Leading and trailing [whitespace] is ignored in parsing inline content:
 
 ```````````````````````````````` example
 #                  foo                     
@@ -1026,6 +1026,20 @@ baz*
 baz</em></h1>
 ````````````````````````````````
 
+The contents are the result of parsing the headings's raw
+content as inlines.  The heading's raw content is formed by
+concatenating the lines and removing initial and final
+[whitespace].
+
+```````````````````````````````` example
+  Foo *bar
+baz*→
+====
+.
+<h1>Foo <em>bar
+baz</em></h1>
+````````````````````````````````
+
 
 The underlining can be any length:
 
@@ -5488,10 +5502,10 @@ Thus, for example, in
 <p><code>hi</code>lo`</p>
 ````````````````````````````````
 
-
 `hi` is parsed as code, leaving the backtick at the end as a literal
 backtick.
 
+
 ## Backslash escapes
 
 Any ASCII punctuation character may be backslash-escaped:
@@ -8686,7 +8700,7 @@ If you want a link after a literal `!`, backslash-escape the
 as the link label.
 
 A [URI autolink](@) consists of `<`, followed by an
-[absolute URI] not containing `<`, followed by `>`.  It is parsed as
+[absolute URI] followed by `>`.  It is parsed as
 a link to the URI, with the URI as the link's label.
 
 An [absolute URI](@),