Fixes for Clang 10 compatibility (closes #965) (#968)

Primarily FrontendAction now gets passed as unique_ptr, but also StringRef was added in a few places. See https://releases.llvm.org/10.0.0/tools/clang/docs/ReleaseNotes.html#internal-api-changes and http://llvm.org/docs/ProgrammersManual.html#the-stringref-class Also, llvm::make_unique is now std::make_unique: https://reviews.llvm.org/D66259 because LLVM requires C++14.

deployment/dockerfiles/linux/centos7_64/Dockerfile

@@ -55,7 +55,7 @@ make -j8 && \
 make -j8 install && rm -Rf /qt
 
 # LLVM/Clang
-ARG LLVM_VERSION=9.0.0
+ARG LLVM_VERSION=10.0.0
 RUN mkdir -p /llvm && cd /llvm && \
 wget http://llvm.org/releases/${LLVM_VERSION}/llvm-${LLVM_VERSION}.src.tar.xz && \
 tar xvf llvm-${LLVM_VERSION}.src.tar.xz && \

deployment/dockerfiles/linux/travis_ci/Dockerfile

@@ -1,4 +1,4 @@
-FROM coatisoftware/centos7_64_qt_llvm:qt5126-llvm900
+FROM coatisoftware/centos7_64_qt_llvm:qt5126-llvm1000
 
 # TODO: remove after full image rebuilt ------------------------------------
 USER root