Auto merge of #2723 - micbou:update-ycmd, r=puremourning

[READY] Update ycmd

This include the following changes:
 - PR https://github.com/Valloric/ycmd/pull/673: update bottle to 0.12.13;
 - PR https://github.com/Valloric/ycmd/pull/790: update Clang to 4.0.1;
 - PR https://github.com/Valloric/ycmd/pull/793: fix compilation with Clang 3.4;
 - PR https://github.com/Valloric/ycmd/pull/796: only configure tests and benchmarks if required;
 - PR https://github.com/Valloric/ycmd/pull/799: fix finding Python library in virtualenv;
 - PR https://github.com/Valloric/ycmd/pull/800: switch back to Boost regex.

Downgrade GCC requirement to 4.8 on Travis.

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.travis.yml

@@ -34,9 +34,9 @@ addons:
     packages:
      - cmake-data
      - cmake
-     # 4.9 is the first version of GCC with good enough C++11 support to build
+     # 4.8 is the first version of GCC with good enough C++11 support to build
      # ycmd.
-     - g++-4.9
+     - g++-4.8
      - ninja-build
      # Everything below is a Python build dep (though it depends on Python
      # version). We need them because pyenv builds Python.

ci/travis/travis_install.linux.sh

@@ -5,8 +5,8 @@
 
 mkdir ${HOME}/bin
 
-ln -s /usr/bin/g++-4.9 ${HOME}/bin/c++
+ln -s /usr/bin/g++-4.8 ${HOME}/bin/c++
-ln -s /usr/bin/gcc-4.9 ${HOME}/bin/cc
+ln -s /usr/bin/gcc-4.8 ${HOME}/bin/cc
 
 export PATH=${HOME}/bin:${PATH}
 

third_party/ycmd

@@ -1 +1 @@
-Subproject commit 490b3ee26d7930704743585ab1ac6f925dbc7202
+Subproject commit 6463774035e61a660ad9150a592b8829eb37fd10