Made vim highlighting work mostly how I want now.

I made `cpp.cplusplus` a hybrid filetype which tricks the vim
highlighting into believing that we're really in raw C++ for the
purposes of the core vim highlighting rules.  My `cplusplus` type
adds more bits to the core stuff, but mostly exists to let
doxygen slip in the way that I want it to.

vim/after/syntax/cplusplus.vim

@@ -1,11 +1,24 @@
+if exists("b:current_syntax")
+  unlet b:current_syntax
+endif
+
+syn include @cxxInDoxygen syntax/cpp.vim
+
+unlet b:current_syntax
 
 " This enables Basic C++ support, with my extensions.
+let c_no_bracket_error=1
+let c_no_curly_error=1
 if version < 600
   so <sfile>:p:h/cpp.vim
 else
   runtime! syntax/cpp.vim
 endif
 
+if exists("b:current_syntax")
+  unlet b:current_syntax
+endif
+
 " This enables doxygen simultaneous with C++.
 if version < 600
   so <sfile>:p:h/doxygen.vim
@@ -13,3 +26,7 @@ else
   runtime! syntax/doxygen.vim
 endif
 
+
+let b:current_syntax = "cplusplus"
+syn sync clear
+syn sync fromstart