Add a "static" before
double mu_timer_real( )
and
double mu_timer_cpu( )
to make sure the minunit.h can work in multiple *.c files in a project.

Signed-off-by: boddmg <boddmg@gmail.com>
Merge pull request #6 from boddmg/master

Fix: Make the minunit.h can work in multiple *.c files in a project.