Rename sphinxcontrib to rubydomain to avoid module loading error

Rename sphinxcontrib to rubydomain to avoid module loading error when
sphinx-build docker image is used.

doc/CMakeLists.txt

@@ -184,9 +184,9 @@ set(EXTRA_DIST
   sources/python-apiref.rst
   sources/building-android-binary.rst
   sources/contribute.rst
-  _exts/sphinxcontrib/LICENSE.rubydomain
-  _exts/sphinxcontrib/__init__.py
-  _exts/sphinxcontrib/rubydomain.py
+  _exts/rubydomain/LICENSE.rubydomain
+  _exts/rubydomain/__init__.py
+  _exts/rubydomain/rubydomain.py
   _themes/sphinx_rtd_theme/__init__.py
   _themes/sphinx_rtd_theme/breadcrumbs.html
   _themes/sphinx_rtd_theme/footer.html

doc/Makefile.am

@@ -206,9 +206,9 @@ EXTRA_DIST = \
 	sources/building-android-binary.rst \
 	sources/contribute.rst \
 	sources/security.rst \
-	_exts/sphinxcontrib/LICENSE.rubydomain \
-	_exts/sphinxcontrib/__init__.py \
-	_exts/sphinxcontrib/rubydomain.py \
+	_exts/rubydomain/LICENSE.rubydomain \
+	_exts/rubydomain/__init__.py \
+	_exts/rubydomain/rubydomain.py \
 	_themes/sphinx_rtd_theme/__init__.py \
 	_themes/sphinx_rtd_theme/breadcrumbs.html \
 	_themes/sphinx_rtd_theme/footer.html \

doc/conf.py.in

@@ -41,7 +41,7 @@ import sys, os
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 #sys.path.insert(0, os.path.abspath('.'))
 
-sys.path.append(os.path.abspath('@top_srcdir@/doc/_exts'))
+sys.path.insert(0, os.path.abspath('@top_srcdir@/doc/_exts'))
 
 # -- General configuration -----------------------------------------------------
 
@@ -50,7 +50,7 @@ sys.path.append(os.path.abspath('@top_srcdir@/doc/_exts'))
 
 # Add any Sphinx extension module names here, as strings. They can be extensions
 # coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
-extensions = ['sphinxcontrib.rubydomain']
+extensions = ['rubydomain.rubydomain']
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['@top_srcdir@/_templates']