Doxyfile.html_cfg: disable clang parsing as default/travis

Signed-off-by: Stephen Arnold <nerdboy@gentoo.org>

.travis.yml

@@ -13,7 +13,6 @@ matrix:
             - ubuntu-toolchain-r-test
           packages:
             - g++-9
-            - clang
             - doxygen
             - graphviz
       compiler: gcc
@@ -27,7 +26,6 @@ matrix:
             - ubuntu-toolchain-r-test
           packages:
             - g++-10
-            - clang
             - doxygen
             - graphviz
       compiler: gcc

Doxyfile.html_cfg

@@ -1026,15 +1026,15 @@ VERBATIM_HEADERS       = YES
 # generated with the -Duse-libclang=ON option for CMake.
 # The default value is: NO.
 
-CLANG_ASSISTED_PARSING = YES
+CLANG_ASSISTED_PARSING = NO
 
 # If clang assisted parsing is enabled you can provide the compiler with command
 # line options that you would normally use when invoking the compiler. Note that
 # the include paths will already be set by doxygen for the files and directories
 # specified with INPUT and INCLUDE_PATH.
 # This tag requires that the tag CLANG_ASSISTED_PARSING is set to YES.
 
-CLANG_OPTIONS          =
+CLANG_OPTIONS          = -std=c++11 -isystem/usr/include/linux
 
 #---------------------------------------------------------------------------
 # Configuration options related to the alphabetical class index