add a std lib test for reading and writing files

* fix fstat wrong on darwin
 * move std.debug.global_allocator to std.debug.global_allocator_state and make it private
 * add std.debug.global_allocator as a pointer (to upgrade your zig code remove
   the '&')
1ac46fac15Andrew Kelley committed on 11/10/2017, 7:17:23 PMparent336d818
13 files changedLine totals unavailable