Allow user to override default values of -x and -std=.
diff --git a/tools/mkdoc.py b/tools/mkdoc.py
index f7048ce..0b0ce3e 100644
--- a/tools/mkdoc.py
+++ b/tools/mkdoc.py
@@ -225,8 +225,12 @@
             job_semaphore.release()
 
 if __name__ == '__main__':
-    parameters = ['-x', 'c++', '-std=c++11']
+    parameters = []
     filenames = []
+    if "-x" not in args:
+        parameters.extend(['-x', 'c++'])
+    if not any(it.startswith("-std=") for it in args):
+        parameters.append('-std=c++11')
 
     if platform.system() == 'Darwin':
         dev_path = '/Applications/Xcode.app/Contents/Developer/'