create a char * argument for umem_cache_create()
create a char * argument for umem_cache_create()

required after the constification in
8f83087f333109ab12d82864b8e7ac98c132cf82

I have no idea why the umem authors did not make this argument
a const, they call strncpy on it

gquintard/Varnish-Cache,gquintard/Varnish-Cache,gquintard/Varnish-Cache,gquintard/Varnish-Cache