fix typo in message

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
add missing include

In file included from measurement/sysfs.cpp:27:
In file included from measurement/../lib.h:59:
In file included from /usr/bin/../lib64/gcc/x86_64-unknown-linux-gnu/4.9.1/../../../../include/c++/4.9.1/string:52:
In file included from /usr/bin/../lib64/gcc/x86_64-unknown-linux-gnu/4.9.1/../../../../include/c++/4.9.1/bits/basic_string.h:2850:
In file included from /usr/bin/../lib64/gcc/x86_64-unknown-linux-gnu/4.9.1/../../../../include/c++/4.9.1/ext/string_conversions.h:41:
/usr/bin/../lib64/gcc/x86_64-unknown-linux-gnu/4.9.1/../../../../include/c++/4.9.1/cstdlib:153:11: error:
      no member named 'realloc' in the global namespace
  using ::realloc;
        ~~^

Signed-off-by: Sami Kerola <kerolasa@iki.fi>