Add Docker for libc++ compile + fix errors

scripts/docker/Ubuntu21

+FROM ubuntu:21.04
+
+RUN export DEBIAN_FRONTEND=noninteractive && apt-get update && \
+    apt-get install -y \
+    cmake \
+    build-essential \
+    pkg-config \
+    casacore-data casacore-dev \
+    libblas-dev liblapack-dev \
+    liblua5.3-dev \
+    libpython3-dev \
+    libboost-date-time-dev libboost-test-dev \
+    libboost-system-dev libboost-filesystem-dev \
+    libgtkmm-3.0-dev \
+    libcfitsio-dev \
+    libfftw3-dev \
+    libgsl-dev \
+    libhdf5-serial-dev \    
+    libpng-dev
+
+ADD . /src
+WORKDIR /src
+
+RUN mkdir /build && cd /build && cmake ../src
+
+RUN cd /build && make -j`nproc --all` && make install && make check -j`nproc --all`
+
+RUN cd /build/python && echo "import aoflagger" | python3

scripts/docker/Ubuntu21-clang-libcxx

+FROM ubuntu:21.04
+
+RUN export DEBIAN_FRONTEND=noninteractive && apt-get update && \
+    apt-get install -y \
+    bison \
+    cmake \
+    build-essential \
+    pkg-config \
+    clang \
+    flex \
+    gfortran \
+    libc++-dev \
+    libc++abi-dev \
+    libblas-dev liblapack-dev \
+    liblua5.3-dev \
+    libpython3-dev \
+    libcfitsio-dev \
+    libfftw3-dev \
+    libgsl-dev \
+    libpng-dev \
+    python3 \
+    python3-distutils \
+    wcslib-dev \
+    wget
+
+RUN \
+    mkdir -p /software && \
+    cd /software && \
+    wget -nv -O - https://boostorg.jfrog.io/artifactory/main/release/1.78.0/source/boost_1_78_0.tar.bz2 | tar xj && \
+    cd boost_1_78_0/ && \
+    ./bootstrap.sh --with-toolset=clang && \
+    ./b2 toolset=clang cxxflags="-stdlib=libc++" linkflags="-stdlib=libc++" install
+
+RUN \
+    mkdir -p /software && \
+    cd /software && \
+    wget -nv -O - https://github.com/HDFGroup/hdf5/archive/refs/tags/hdf5-1_12_1.tar.gz | tar xz && \
+    cd /software/hdf5-hdf5-1_12_1 && \
+    CC=/usr/bin/clang CXX=/usr/bin/clang++ CXXFLAGS="-stdlib=libc++" LDFLAGS="-stdlib=libc++" ./configure --prefix /usr/local --enable-cxx && \
+    make -j`nproc` install
+
+RUN \
+    mkdir -p /software/casacore/build && \
+    cd /software/casacore && \
+    wget -nv -O - https://github.com/casacore/casacore/archive/refs/tags/v3.4.0.tar.gz | tar xz && \
+    cd build && \
+    cmake \
+      -DBUILD_TESTING=OFF -DCMAKE_C_COMPILER=/usr/bin/clang -DCMAKE_CXX_COMPILER=/usr/bin/clang++ -DCMAKE_CXX_FLAGS="-stdlib=libc++" \
+      -DBUILD_PYTHON=OFF -DBUILD_PYTHON3=OFF \
+      ../casacore-3.4.0 && \
+    make install -j`nproc`
+
+ADD . /src
+WORKDIR /src
+
+RUN mkdir /build && cd /build && cmake ../src -DCMAKE_C_COMPILER=/usr/bin/clang -DCMAKE_CXX_COMPILER=/usr/bin/clang++ -DCMAKE_CXX_FLAGS="-stdlib=libc++"
+
+RUN cd /build && make -j`nproc --all` && make install && make check -j`nproc --all`
+
+RUN cd /build/python && echo "import aoflagger" | python3

util/numberparser.h

-#include <stdexcept>
-
 #include <cmath>
+#include <stdexcept>
+#include <string>
 
 #ifndef HAVE_EXP10
 #define exp10(x) exp((2.3025850929940456840179914546844) * (x))