[depr.strstreambuf.virtuals] Fix a collection of formatting issues (paragraph

numbers in the middle of a bullet in the middle of a paragraph, half of a
paragraph accidentally incorporated into a table, missing begin/end of bulleted
list).

Fixes #381.

Author: zygoloid

source/future.tex

@@ -602,15 +602,14 @@
 assigns \tcode{c} to
 \tcode{*pnext++}.
 
-\pnum
 Returns
 \tcode{(unsigned char)c}.
+
 \item
 If
 \tcode{c == EOF},
 there is no character to append.
 
-\pnum
 Returns a value other than \tcode{EOF}.
 \end{itemize}
 
@@ -679,7 +678,6 @@
 \tcode{gnext - 1}
 to \tcode{gnext}.
 
-\pnum
 Returns \tcode{c}.
 \item
 If
@@ -689,7 +687,6 @@
 assigns \tcode{c} to
 \tcode{*\dcr{}gnext}.
 
-\pnum
 Returns
 \tcode{c}.
 \item
@@ -700,7 +697,6 @@
 \tcode{gnext - 1}
 to \tcode{gnext}.
 
-\pnum
 Returns a value other than
 \tcode{EOF}.
 \end{itemize}
@@ -745,7 +741,6 @@
 assigning to \tcode{gend} a value greater than \tcode{gnext} and
 no greater than \tcode{pnext}.
 
-\pnum
 Returns \tcode{(unsigned char*)gnext}.
 \end{itemize}
 
@@ -801,17 +796,15 @@
 \tcode{way == ios::cur}	&
  the next pointer minus the beginning pointer (\tcode{xnext - xbeg}).	\\ \rowsep
 \tcode{way == ios::end}	&
- \tcode{seekhigh} minus the beginning pointer (\tcode{seekhigh - xbeg}).\\ \rowsep
-If \tcode{(newoff + off) <}\br
-\tcode{(seeklow - xbeg)},\br
-or \tcode{(seekhigh - xbeg) <}\br
-\tcode{(newoff + off)}			&
- the positioning operation fails	\\
+ \tcode{seekhigh} minus the beginning pointer (\tcode{seekhigh - xbeg}).	\\
 \end{libtab2}
 
 \pnum
+If \tcode{(newoff + off) < (seeklow - xbeg)}
+or \tcode{(seekhigh - xbeg) < (newoff + off)},
+the positioning operation fails.
 Otherwise, the function assigns
-\tcode{xbeg} + \tcode{newoff} + \tcode{off}
+\tcode{xbeg + newoff + off}
 to the next pointer \tcode{xnext}.
 
 \pnum
@@ -851,12 +844,14 @@
 positions the output sequence.
 \item
 If the function positions neither sequence, the positioning operation fails.
+\end{itemize}
 
 \pnum
 For a sequence to be positioned, if its next pointer is a null pointer,
 the positioning operation fails.
 Otherwise, the function determines \tcode{newoff} from
 \tcode{sp.offset()}:
+\begin{itemize}
 \item
 If \tcode{newoff} is an invalid stream position,
 has a negative value, or