Update all remaining targets to Ubuntu 18.04

Author: gnzlbg

ci/docker/aarch64-unknown-linux-gnu/Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:17.10
+FROM ubuntu:18.04
 RUN apt-get update && apt-get install -y --no-install-recommends \
   gcc libc6-dev ca-certificates \
   gcc-aarch64-linux-gnu libc6-dev-arm64-cross qemu-user

ci/docker/arm-unknown-linux-gnueabihf/Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:17.10
+FROM ubuntu:18.04
 RUN apt-get update && apt-get install -y --no-install-recommends \
   gcc libc6-dev ca-certificates \
   gcc-arm-linux-gnueabihf libc6-dev-armhf-cross qemu-user

ci/docker/asmjs-unknown-emscripten/Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:16.04
+FROM ubuntu:18.04
 
 RUN apt-get update && \
     apt-get install -y --no-install-recommends \

ci/docker/mips-unknown-linux-gnu/Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:17.10
+FROM ubuntu:18.04
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
         gcc libc6-dev qemu-user ca-certificates \

ci/docker/mips64-unknown-linux-gnuabi64/Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:17.10
+FROM ubuntu:18.04
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
         gcc libc6-dev qemu-user ca-certificates \

ci/docker/mips64el-unknown-linux-gnuabi64/Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:17.10
+FROM ubuntu:18.04
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
         gcc libc6-dev qemu-user ca-certificates \

ci/docker/s390x-unknown-linux-gnu/Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:17.10
+FROM ubuntu:18.04
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
         curl ca-certificates \

ci/docker/wasm32-unknown-emscripten/Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:16.04
+FROM ubuntu:18.04
 
 RUN apt-get update && \
     apt-get install -y --no-install-recommends \