[Bug #1579796] Wrong syntax for PyDateTime_IMPORT in documentation. Reported by David Faure.

Doc/api/concrete.tex

@@ -2879,10 +2879,10 @@ rather than explicitly calling \cfunction{PyGen_New}.
 Various date and time objects are supplied by the \module{datetime}
 module.  Before using any of these functions, the header file
 \file{datetime.h} must be included in your source (note that this is
-not include by \file{Python.h}), and macro \cfunction{PyDateTime_IMPORT()}
-must be invoked.  The macro arranges to put a pointer to a C structure
-in a static variable \code{PyDateTimeAPI}, which is used by the following
-macros.
+not included by \file{Python.h}), and the macro
+\cfunction{PyDateTime_IMPORT} must be invoked.  The macro puts a
+pointer to a C structure into a static variable, 
+\code{PyDateTimeAPI}, that is used by the following macros.
 
 Type-check macros: