Travis upgrade to GCC 10 and Clang 10

Upgrade to latest and greatest toolchains.

.travis.yml

@@ -57,33 +57,33 @@ jobs:
           apt:
             sources:
               - sourceline: 'ppa:ubuntu-toolchain-r/test'
-              - sourceline: 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-9 main'
+              - sourceline: 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-10 main'
                 key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'
             packages:
-              - clang-9
+              - clang-10
         env:
-          - CC=clang-9
-          - CXX=clang++-9
+          - CC=clang-10
+          - CXX=clang++-10
           - CMAKE_ARGS="-DPYTHON_EXECUTABLE=/usr/bin/python3 -DBUILD_FEM_NETGEN=ON -DBUILD_QT5=ON"
           - CACHE_NAME=JOB1
 
       - os: linux
         dist: bionic
         language: cpp
-        compiler: gcc-9
+        compiler: gcc-10
         cache: ccache
         addons:
           apt:
             sources:
               - sourceline: 'ppa:ubuntu-toolchain-r/test'
             packages:
-              - gcc-9
-              - g++-9
+              - gcc-10
+              - g++-10
         env:
-          - CC=gcc-9
-          - CXX=g++-9
-          - CC_FOR_BUILD=gcc-9
-          - CXX_FOR_BUILD=g++-9
+          - CC=gcc-10
+          - CXX=g++-10
+          - CC_FOR_BUILD=gcc-10
+          - CXX_FOR_BUILD=g++-10
           - CMAKE_ARGS="-DCMAKE_CXX_COMPILER=/usr/bin/c++ -DCMAKE_C_COMPILER=/usr/bin/cc -DPYTHON_EXECUTABLE=/usr/bin/python3 -DBUILD_FEM_NETGEN=ON -DBUILD_QT5=ON"
           - CACHE_NAME=JOB2