init.c: adding ifdef to limit the use of syscall function in some systems.

The syscall function will be used only when the system is defined as linux.
For gnumach for example, the syscall function is defined in another file or
or path. So, it has a special case to be considered.

Signed-off-by: Julio Faracco <jcfaracco@gmail.com>
tests: adding time.h file to avoid warning in sorts.c test.

sorts.c is missing time.h in include header. This is throwing an "implicit
declaration" warning.

Signed-off-by: Julio Faracco <jcfaracco@gmail.com>