Fix sphinx-doc#777 (part II): Latex output "too deeply nested"

Patch use of quote environment by LaTeX writer to prevent increase of
``\@listdepth``.

This is experimental and probably not good (Jun 5, 2016).
Rebased on master at 0ad5420 (Oct 25, 2016).

sphinx/texinputs/sphinx.sty

@@ -1001,3 +1001,7 @@
 \providecommand*{\sphinxtableofcontents}{\tableofcontents}
 \providecommand*{\sphinxthebibliography}{\thebibliography}
 \providecommand*{\sphinxtheindex}{\theindex}
+
+% will be used to accompany quote environment and help avoid "too deeply nested"
+\newcommand*\SphinxDecreaseListDepth {\global\advance\@listdepth\m@ne}
+\newcommand*\SphinxIncreaseListDepth {\global\advance\@listdepth\@ne}

sphinx/writers/latex.py

@@ -1304,12 +1304,14 @@ def depart_definition(self, node):
         self.body.append('\n')
 
     def visit_field_list(self, node):
-        self.body.append('\\begin{quote}\\begin{description}\n')
+        self.body.append('\\begin{quote}\\SphinxDecreaseListDepth'
+                         '\\begin{description}\n')
         if self.table:
             self.table.has_problematic = True
 
     def depart_field_list(self, node):
-        self.body.append('\\end{description}\\end{quote}\n')
+        self.body.append('\\end{description}\\end{quote}'
+                         '\\SphinxIncreaseListDepth\n')
 
     def visit_field(self, node):
         pass
@@ -1960,7 +1962,7 @@ def visit_block_quote(self, node):
                     isinstance(child, nodes.enumerated_list):
                 done = 1
         if not done:
-            self.body.append('\\begin{quote}\n')
+            self.body.append('\\begin{quote}\\SphinxDecreaseListDepth\n')
             if self.table:
                 self.table.has_problematic = True
 
@@ -1972,7 +1974,7 @@ def depart_block_quote(self, node):
                     isinstance(child, nodes.enumerated_list):
                 done = 1
         if not done:
-            self.body.append('\\end{quote}\n')
+            self.body.append('\\end{quote}\\SphinxIncreaseListDepth\n')
 
     # option node handling copied from docutils' latex writer