Enable compiler sanitizers on Travis

[PJK]

Currently annoying to do due to old binutils, which results in linker issues (see e.g. Project-OSRM/osrm-backend#3216)

/usr/bin/gcc-6 -fPIC  -std=c99 -g -O0 -Wall -pedantic -g -ggdb -DDEBUG=true -fsanitize=address -fsanitize=bounds -fsanitize=alignment  -shared -Wl,-soname,libcbor.so.0.5.0 -o libcbor.so.0.5.0 CMakeFiles/cbor_shared.dir/cbor.c.o CMakeFiles/cbor_shared.dir/cbor/streaming.c.o CMakeFiles/cbor_shared.dir/cbor/internal/encoders.c.o CMakeFiles/cbor_shared.dir/cbor/internal/builder_callbacks.c.o CMakeFiles/cbor_shared.dir/cbor/internal/loaders.c.o CMakeFiles/cbor_shared.dir/cbor/internal/memory_utils.c.o CMakeFiles/cbor_shared.dir/cbor/internal/stack.c.o CMakeFiles/cbor_shared.dir/cbor/internal/unicode.c.o CMakeFiles/cbor_shared.dir/cbor/encoding.c.o CMakeFiles/cbor_shared.dir/cbor/serialization.c.o CMakeFiles/cbor_shared.dir/cbor/arrays.c.o CMakeFiles/cbor_shared.dir/cbor/common.c.o CMakeFiles/cbor_shared.dir/cbor/floats_ctrls.c.o CMakeFiles/cbor_shared.dir/cbor/bytestrings.c.o CMakeFiles/cbor_shared.dir/cbor/callbacks.c.o CMakeFiles/cbor_shared.dir/cbor/strings.c.o CMakeFiles/cbor_shared.dir/cbor/maps.c.o CMakeFiles/cbor_shared.dir/cbor/tags.c.o CMakeFiles/cbor_shared.dir/cbor/ints.c.o CMakeFiles/cbor_shared.dir/allocators.c.o 
/usr/bin/x86_64-linux-gnu-ld: unrecognized option '--push-state'