Support CPython builds with docstrings disabled by wrapping docstring literals...

Support CPython builds with docstrings disabled by wrapping docstring literals in the `PyDoc_STR()` macro.
Closes GH-884.

Cython/Compiler/ModuleNode.py

@@ -2209,7 +2209,7 @@ class ModuleNode(Nodes.Node, Nodes.BlockNode):
                 if doc:
                     if doc.is_unicode:
                         doc = doc.as_utf8_string()
-                    doc_code = doc.as_c_string_literal()
+                    doc_code = "PyDoc_STR(%s)" % doc.as_c_string_literal()
                 else:
                     doc_code = "0"
                 code.putln(

Cython/Compiler/Nodes.py

@@ -3483,7 +3483,7 @@ class DefNodeWrapper(FuncDefNode):
                 docstr = docstr.as_utf8_string()
 
             if not (entry.is_special and entry.name in ('__getbuffer__', '__releasebuffer__')):
-                code.putln('static char %s[] = %s;' % (
+                code.putln('PyDoc_STRVAR(%s, %s);' % (
                     entry.doc_cname,
                     docstr.as_c_string_literal()))
 

Cython/Compiler/TypeSlots.py

@@ -446,7 +446,7 @@ class DocStringSlot(SlotDescriptor):
             return "0"
         if doc.is_unicode:
             doc = doc.as_utf8_string()
-        return doc.as_c_string_literal()
+        return "PyDoc_STR(%s)" % doc.as_c_string_literal()
 
 
 class SuiteSlot(SlotDescriptor):