Benchmark for measuring TLS access performance

This patch adds a tool, tests/misc-tls.cc, for quanitifying issue #555.
I.e., this tool can help us measure how much slower is access to TLS
variables in an OSv application (compiled as shared object) compared
to a Linux application.

The results of this benchmark on my laptop is as follows: In a simple
loop accessing a global variable, the iteration length was 2 ns.
In Linux, switching to a thread-local variable did not noticably change
the iteration length. But in OSv, changing the variable to a thread-local
one dramatically increases the iteration length to 27 nanoseconds.

Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
cli: Add options 'R' and 'a' to command ls

cli: Add option to recursively list subdirectories, fix option 'a'

Signed-off-by: Nehal J Wani <nehaljw.kkd1@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>