Removed vestigial restriction in list item spec.

The "not separated by more than one blank line" was a left-over
from an earlier version of the spec in which two blank lines
ended a list.

Closes #543.

spec.txt

@@ -3696,9 +3696,8 @@ in some browsers.)
 The following rules define [list items]:
 
 1.  **Basic case.**  If a sequence of lines *Ls* constitute a sequence of
-    blocks *Bs* starting with a [non-whitespace character] and not separated
-    from each other by more than one blank line, and *M* is a list
-    marker of width *W* followed by 1 ≤ *N* ≤ 4 spaces, then the result
+    blocks *Bs* starting with a [non-whitespace character], and *M* is a
+    list marker of width *W* followed by 1 ≤ *N* ≤ 4 spaces, then the result
     of prepending *M* and the following spaces to the first line of
     *Ls*, and indenting subsequent lines of *Ls* by *W + N* spaces, is a
     list item with *Bs* as its contents.  The type of the list item
@@ -4008,8 +4007,7 @@ A start number may not be negative:
 
 2.  **Item starting with indented code.**  If a sequence of lines *Ls*
     constitute a sequence of blocks *Bs* starting with an indented code
-    block and not separated from each other by more than one blank line,
-    and *M* is a list marker of width *W* followed by
+    block, and *M* is a list marker of width *W* followed by
     one space, then the result of prepending *M* and the following
     space to the first line of *Ls*, and indenting subsequent lines of
     *Ls* by *W + 1* spaces, is a list item with *Bs* as its contents.