Add docs build.

docs/Doxyfile

@@ -58,7 +58,7 @@ PROJECT_LOGO           =
 # entered, it will be relative to the location where doxygen was started. If
 # left blank the current directory will be used.
 
-OUTPUT_DIRECTORY       = .
+OUTPUT_DIRECTORY       = doxydocs
 
 # If the CREATE_SUBDIRS tag is set to YES then doxygen will create 4096 sub-
 # directories (in 2 levels) under the output directory of each output format and
@@ -836,7 +836,7 @@ WARN_NO_PARAMDOC       = NO
 # Possible values are: NO, YES and FAIL_ON_WARNINGS.
 # The default value is: NO.
 
-WARN_AS_ERROR          = NO
+WARN_AS_ERROR          = YES
 
 # The WARN_FORMAT tag determines the format of the warning messages that doxygen
 # can produce. The string should contain the $file, $line, and $text tags, which