[SYCL] Improve Doxygen documentation UX (#1201)

- Fix classes missing due to inline namespace macro.
- Enable first sentence as brief.
- Make diagrams clickable.

Signed-off-by: Alexander Batashev <alexander.batashev@intel.com>

Author: Alexander Batashev

sycl/doc/doxygen.cfg.in

@@ -187,15 +187,15 @@ SHORT_NAMES            = NO
 # description.)
 # The default value is: NO.
 
-JAVADOC_AUTOBRIEF      = NO
+JAVADOC_AUTOBRIEF      = YES
 
 # If the QT_AUTOBRIEF tag is set to YES then doxygen will interpret the first
 # line (until the first dot) of a Qt-style comment as the brief description. If
 # set to NO, the Qt-style will behave just like regular Qt-style comments (thus
 # requiring an explicit \brief command for a brief description.)
 # The default value is: NO.
 
-QT_AUTOBRIEF           = NO
+QT_AUTOBRIEF           = YES
 
 # The MULTILINE_CPP_IS_BRIEF tag can be set to YES to make doxygen treat a
 # multi-line C++ special comment block (i.e. a block of //! or /// comments) as
@@ -2061,15 +2061,15 @@ ENABLE_PREPROCESSING   = YES
 # The default value is: NO.
 # This tag requires that the tag ENABLE_PREPROCESSING is set to YES.
 
-MACRO_EXPANSION        = NO
+MACRO_EXPANSION        = YES
 
 # If the EXPAND_ONLY_PREDEF and MACRO_EXPANSION tags are both set to YES then
 # the macro expansion is limited to the macros specified with the PREDEFINED and
 # EXPAND_AS_DEFINED tags.
 # The default value is: NO.
 # This tag requires that the tag ENABLE_PREPROCESSING is set to YES.
 
-EXPAND_ONLY_PREDEF     = NO
+EXPAND_ONLY_PREDEF     = YES
 
 # If the SEARCH_INCLUDES tag is set to YES, the include files in the
 # INCLUDE_PATH will be searched if a #include is found.
@@ -2101,7 +2101,7 @@ INCLUDE_FILE_PATTERNS  =
 # recursively expanded use the := operator instead of the = operator.
 # This tag requires that the tag ENABLE_PREPROCESSING is set to YES.
 
-PREDEFINED             =
+PREDEFINED             = "__SYCL_INLINE_NAMESPACE(X)=namespace X"
 
 # If the MACRO_EXPANSION and EXPAND_ONLY_PREDEF tags are set to YES then this
 # tag can be used to specify a list of macro names that should be expanded. The
@@ -2390,7 +2390,7 @@ DOT_IMAGE_FORMAT       = @DOT_IMAGE_FORMAT@
 # The default value is: NO.
 # This tag requires that the tag HAVE_DOT is set to YES.
 
-INTERACTIVE_SVG        = NO
+INTERACTIVE_SVG        = YES
 
 # The DOT_PATH tag can be used to specify the path where the dot tool can be
 # found. If left blank, it is assumed the dot tool can be found in the path.