Fix definition of reserved fields in the GOT

Three instead of two fields are actually reserved at the start of the GOT.
Reflect that.  Also replace "word" by "doubleword" when referring to
8-byte fields in the GOT.

lzsabi.tex

@@ -4828,19 +4828,20 @@ \subsection{Global Offset Table}
 
 The format and interpretation of the Global Offset Table is processor
 specific.  For \ABINAME{} the symbol \texttt{\_GLOBAL\_OFFSET\_TABLE\_}
-may be used to access the table.  The symbol refers to the start of
-the \texttt{.got} section.  Two words in the GOT are reserved:
+may be used to access the table.  The symbol refers to the start of the
+\texttt{.got} section.  The first three \ifzseries double\fi words in the
+GOT are reserved:
 \begin{itemize}
-\item The word at \texttt{\_GLOBAL\_OFFSET\_TABLE\_[0]} is set by the
-  linkage editor to hold the address of the dynamic structure,
-  referenced with the symbol \texttt{\_DYNAMIC}.  This allows a
-  program, such as the dynamic linker, to find its own dynamic
-  structure without having yet processed its relocation entries.  This
-  is especially important for the dynamic linker, because it must
-  initialize itself without relying on other programs to relocate its
-  memory image.
-\item The word at \texttt{\_GLOBAL\_OFFSET\_TABLE\_[1]} is reserved
-  for future use.
+\item The \ifzseries double\fi word at
+  \texttt{\_GLOBAL\_OFFSET\_TABLE\_[0]} is set by the linkage editor to
+  hold the address of the dynamic structure, referenced with the symbol
+  \texttt{\_DYNAMIC}.  This allows a program, such as the dynamic linker,
+  to find its own dynamic structure without having yet processed its
+  relocation entries.  This is especially important for the dynamic
+  linker, because it must initialize itself without relying on other
+  programs to relocate its memory image.
+\item The \ifzseries double\fi words at
+  \texttt{\_GLOBAL\_OFFSET\_TABLE\_[1...2]} are reserved for system use.
 \end{itemize}
 
 The Global Offset Table resides in the ELF \texttt{.got} section.