Travis CI: switch macOS builds to xcode10.1 image
Travis CI: switch macOS builds to xcode10.1 image

xcode10.0 seems to have Homebrew broken, and xcode9.4 has a problem with
SSLSetALPNProtocols (see also commit
f545d181ade8736dfda93e8abb34ab93ac34e931).

QMatrixClient/libqmatrixclient,Fxrh/libqmatrixclient,QMatrixClient/libqmatrixclient