ARROW-4274: [C++][Gandiva] split decimal into two parts

Author: Pindikura Ravindra <ravindra@dremio.com>
Author: Antoine Pitrou <antoine@python.org>

Closes apache#3414 from pravindra/split and squashes the following commits:

c96fbbf <Antoine Pitrou> Try to fix MSVC compile failure
ed7e110 <Antoine Pitrou> Try to use newer Sphinx and breathe versions when building the docs
2c0d870 <Pindikura Ravindra> ARROW-4274: Fix doxygen error
e2de415 <Pindikura Ravindra> ARROW-4274: Add empty constructor for older compilers
42549b0 <Pindikura Ravindra> ARROW-4274: Address review comments
49d7933 <Pindikura Ravindra> ARROW-4274: Misc cleanups in header files
18050f8 <Pindikura Ravindra> ARROW-4274: split decimal into two parts

.travis.yml

@@ -131,13 +131,12 @@ matrix:
     - $TRAVIS_BUILD_DIR/ci/travis_install_toolchain.sh
     script:
     - $TRAVIS_BUILD_DIR/ci/travis_script_java.sh || travis_terminate 1
+    - ARROW_TRAVIS_PYTHON_GANDIVA=1
     # Only run Plasma tests with valgrind in one of the Python builds because
     # they are slow
     - export PLASMA_VALGRIND=0
     - $TRAVIS_BUILD_DIR/ci/travis_script_python.sh 2.7 || travis_terminate 1
     - export PLASMA_VALGRIND=1
-    # Gandiva tests are not enabled with python 2.7
-    - ARROW_TRAVIS_PYTHON_GANDIVA=1
     - $TRAVIS_BUILD_DIR/ci/travis_script_python.sh 3.6 || travis_terminate 1
     - $TRAVIS_BUILD_DIR/ci/travis_upload_cpp_coverage.sh
   - name: "[OS X] C++ w/ XCode 8.3"

ci/conda_env_sphinx.yml

@@ -16,8 +16,7 @@
 # under the License.
 
 # Requirements for building the documentation
-breathe
+# You also need to `pip install -r docs/requirements.txt`
+
 doxygen
 ipython
-sphinx
-sphinx_rtd_theme

ci/travis_script_python.sh

@@ -62,6 +62,7 @@ which python
 if [ "$ARROW_TRAVIS_PYTHON_DOCS" == "1" ] && [ "$PYTHON_VERSION" == "3.6" ]; then
   # Install documentation dependencies
   conda install -y --file ci/conda_env_sphinx.yml
+  pip install -q -r docs/requirements.txt
 fi
 
 # ARROW-2093: PyTorch increases the size of our conda dependency stack
@@ -124,7 +125,7 @@ $ARROW_CPP_BUILD_DIR/$ARROW_BUILD_TYPE/arrow-python-test
 pushd $ARROW_PYTHON_DIR
 
 # Other stuff pip install
-pip install -r requirements.txt
+pip install -q -r requirements.txt
 
 if [ "$PYTHON_VERSION" == "3.6" ]; then
     pip install -q pickle5
@@ -134,6 +135,9 @@ if [ "$ARROW_TRAVIS_COVERAGE" == "1" ]; then
     pip install -q coverage
 fi
 
+echo "=== pip list ==="
+pip list
+
 export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:$ARROW_CPP_INSTALL/lib/pkgconfig
 
 export PYARROW_BUILD_TYPE=$ARROW_BUILD_TYPE

cpp/src/arrow/CMakeLists.txt

@@ -101,6 +101,7 @@ set(ARROW_SRCS
   io/memory.cc
   io/readahead.cc
 
+  util/basic_decimal.cc
   util/bit-util.cc
   util/compression.cc
   util/cpu-info.cc