LaTeX writer: include cmap package by default.

Also, fix a small typo in config.rst.

doc/config.rst

@@ -1077,7 +1077,7 @@ These options influence LaTeX output.
         "Rejne".  You can also set this to ``''`` to disable fncychap.
      ``'preamble'``
         Additional preamble content, default empty.
-     ``'footer'```
+     ``'footer'``
         Additional footer content (before the indices), default empty.
 
    * Keys that don't need be overridden unless in special cases are:
@@ -1085,6 +1085,8 @@ These options influence LaTeX output.
      ``'inputenc'``
         "inputenc" package inclusion, default
         ``'\\usepackage[utf8]{inputenc}'``.
+     ``'cmappkg'``
+        "cmap" package inclusion, default ``'\\usepackage{cmap}'``.
      ``'fontenc'``
         "fontenc" package inclusion, default ``'\\usepackage[T1]{fontenc}'``.
      ``'maketitle'``

sphinx/writers/latex.py

@@ -34,6 +34,7 @@ HEADER = r'''%% Generated by Sphinx.
 \documentclass[%(papersize)s,%(pointsize)s%(classoptions)s]{%(wrapperclass)s}
 %(inputenc)s
 %(utf8extra)s
+%(cmappkg)s
 %(fontenc)s
 %(babel)s
 %(fontpkg)s
@@ -138,6 +139,7 @@ class LaTeXTranslator(nodes.NodeVisitor):
         'extraclassoptions': '',
         'inputenc':        '\\usepackage[utf8]{inputenc}',
         'utf8extra':       '\\DeclareUnicodeCharacter{00A0}{\\nobreakspace}',
+        'cmappkg':         '\\usepackage{cmap}\n',
         'fontenc':         '\\usepackage[T1]{fontenc}',
         'babel':           '\\usepackage{babel}',
         'fontpkg':         '\\usepackage{times}',