test: fix VC++ warning C4244
linux: include grp.h for setgroups()
unix, windows: add uv_loop_init and uv_loop_close

These functions supersede uv_loop_new and uv_loop_delete.
uv_loop_init initialized a user allocated loop and uv_loop_close
removes all associated resources a loop uses after it has finished
execution.

uv_loop_new and uv_loop_delete are now deprecated.
unix, windows: add uv_getrusage() function
test: fix spawn_stdout_and_stderr_to_file test

S_IREAD and S_IWRITE are obsolete in GNU libs and
not included in the Android NDK's libc. See
http://www.gnu.org/savannah-checkouts/gnu/libc
/manual/html_node/Permission-Bits.html
build: update android toolchain

gcc-4.7 has been removed in revision r9c. More info:
http://developer.android.com/tools/sdk/ndk/index.html#Revisions