Add highlight_options configuration value

This changeset adds the `highlight_options` configuration value, which
specifies a dict of key-value pairs to pass to the Pygments highlighter
specified with `highlight_language`. For example, specifying
`highlight_options = {'funcnamehighlighting' : False}` for the 'php'
lexer will disable function name highlighting.
Both the HTML and LaTeX writers have been updated to include the
options when calling `highlight_block()`, as long as the currently
selected language matches what was set with `highlight_language`, i.e.
not when modified by `highlight::` or `code-block::` directives.

doc/config.rst

@@ -303,9 +303,17 @@ Project information
 
    .. versionadded:: 0.5
 
+.. confval:: highlight_options
+
+   A dictionary of options that modify the behavior of the lexer for the
+   selected language. These are lexer-specific. For the options understood by
+   each, see the `Pygments documentation <http://pygments.org/docs/lexers/>`_.
+
+   .. versionadded:: 1.3
+
 .. confval:: pygments_style
 
-   The style name to use for Pygments highlighting of source code.  The default
+   The style name to use for Pygments highlighting of source code.  The given
    style is selected by the theme for HTML output, and ``'sphinx'`` otherwise.
 
    .. versionchanged:: 0.3