Doc: fix warnings with Doxygen 1.9.3

Doxyfile

@@ -1003,15 +1003,6 @@ EXTERNAL_GROUPS        = YES
 # Configuration options related to the dot tool
 #---------------------------------------------------------------------------
 
-# If the CLASS_DIAGRAMS tag is set to YES (the default) Doxygen will
-# generate a inheritance diagram (in HTML, RTF and LaTeX) for classes with base
-# or super classes. Setting the tag to NO turns the diagrams off. Note that
-# this option is superseded by the HAVE_DOT option below. This is only a
-# fallback. It is recommended to install and use dot, since it yields more
-# powerful graphs.
-
-CLASS_DIAGRAMS         = YES
-
 # If set to YES, the inheritance and collaboration graphs will hide
 # inheritance and usage relations if the target is undocumented
 # or is not a class.

ogr/ogr_api.h

@@ -610,8 +610,6 @@ OGRErr CPL_DLL OGR_L_SetAttributeFilter( OGRLayerH, const char * );
 void   CPL_DLL OGR_L_ResetReading( OGRLayerH );
 OGRFeatureH CPL_DLL OGR_L_GetNextFeature( OGRLayerH ) CPL_WARN_UNUSED_RESULT;
 
-/*! @endcond */
-
 /** Conveniency macro to iterate over features of a layer.
  *
  * Typical usage is:

ogr/ogrct.cpp

@@ -1080,7 +1080,6 @@ OGRProjCT::OGRProjCT()
 /*                  OGRProjCT(const OGRProjCT& other)                   */
 /************************************************************************/
 
-//! @cond Doxygen_Suppress
 OGRProjCT::OGRProjCT(const OGRProjCT& other) :
     poSRSSource((other.poSRSSource != nullptr) ? (other.poSRSSource->Clone()) : (nullptr)),
     bSourceLatLong(other.bSourceLatLong),

port/cpl_path.cpp

@@ -938,8 +938,8 @@ const char *CPLExtractRelativePath( const char *pszBaseDir,
  * <pre>
  * CPLCleanTrailingSlash( "abc/def/" ) == "abc/def"
  * CPLCleanTrailingSlash( "abc/def" ) == "abc/def"
- * CPLCleanTrailingSlash( "c:\abc\def\" ) == "c:\abc\def"
- * CPLCleanTrailingSlash( "c:\abc\def" ) == "c:\abc\def"
+ * CPLCleanTrailingSlash( "c:\\abc\\def\\" ) == "c:\\abc\\def"
+ * CPLCleanTrailingSlash( "c:\\abc\\def" ) == "c:\\abc\\def"
  * CPLCleanTrailingSlash( "abc" ) == "abc"
  * </pre>
  *