Use API_VERSION_NUMBER for debug help API version check.

This symbol is not documented but seems to be defined in all the existing
versions of imagehlp.h, so use it instead of relying on a hack with checkng
whether DBHLPAPI symbol is defined.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73793 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/doxygen/mainpages/const_wxusedef.h

@@ -91,7 +91,7 @@ library:
 @itemdef{wxUSE_DATAVIEWCTRL, Use wxDataViewCtrl class.}
 @itemdef{wxUSE_DATEPICKCTRL, Use wxDatePickerCtrl class.}
 @itemdef{wxUSE_DATETIME, Use wxDateTime and related classes.}
-@itemdef{wxUSE_DBGHELP, Use wxDbgHelpDLL class.}
+@itemdef{wxUSE_DBGHELP, Predefine as 0 to avoid using wxDbgHelpDLL and related classes.}
 @itemdef{wxUSE_DC_TRANSFORM_MATRIX, Use wxDC::SetTransformMatrix() and related methods.}
 @itemdef{wxUSE_DEBUG_CONTEXT, Use wxDebugContext class.}
 @itemdef{wxUSE_DEBUG_NEW_ALWAYS, See @ref overview_debugging}