Update CI from ubuntu 16.04 (EOL) to 19.04

Closes #1333 .

See https://github.com/rust-lang/rust/pull/60775 .

[breaking change] PTRACE_GETFPXREGS and PTRACE_SETFPXREGS were incorrectly re-exported on arm but they are x86 specific

These types have a p_types field, but the resolv.h
header defines p_types __p_types macro that breaks them.