Remove configuration of HAVE_PUTENV.

The Python includes files for Windows define HAVE_PUTENV to be
empty. GnuCash under MINGW (only) defines it to be 1. This causes
redefinition errors when building the Python bindings on Windows.
HAVE_PUTENV is not used in the GnuCash code base, so the best
solution seems to be to just get rid of it.

src/CMakeLists.txt

@@ -13,10 +13,6 @@ IF (WIN32)
   SET (HAVE_HTMLHELPW 1)
 ENDIF (WIN32)
 
-IF (MINGW)
-  SET (HAVE_PUTENV 1)
-ENDIF (MINGW)
-
 CHECK_INCLUDE_FILES (X11/Xlib.h HAVE_X11_XLIB_H)
 CHECK_INCLUDE_FILES (dirent.h HAVE_DIRENT_H)
 CHECK_INCLUDE_FILES (dlfcn.h HAVE_DLFCN_H)

src/config.h.cmake.in

@@ -197,9 +197,6 @@
 /* Have PTHREAD_PRIO_INHERIT. */
 #cmakedefine HAVE_PTHREAD_PRIO_INHERIT 1
 
-/* Define to 1 if you have the `putenv' function. */
-#cmakedefine HAVE_PUTENV 1
-
 /* If available, contains the Python version number currently in use. */
 #cmakedefine HAVE_PYTHON 1