perf map: Use strstarts() to look for Android libraries

perf map: Use strstarts() to look for Android libraries

And add the '/' to avoid looking at things like "/system/libsomething",
when all we want to know if it is like "/system/lib/something", i.e. if
it is in that system library dir.

Using strstarts() avoids off-by-one errors like recently fixed in this
file.

Since this adds the '/' I separated this patch, another patch will make
this consistent by removing other strncmp(str, prefix, manually
calculated prefix length) usage.

Reported-by: Dominik Czarnota <dominik.b.czarnota@gmail.com>
Acked-by: Dominik Czarnota <dominik.b.czarnota@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lore.kernel.org/lkml/CABEVAa0_q-uC0vrrqpkqRHy_9RLOSXOJxizMLm1n5faHRy2AeA@mail.gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>