build: add support for VS2013
test: allow UV_EACCES in spawn_fails

Allow UV_EACCES as a successful return value when uv_spawn fails.

When the PATH environment variable contains a directory which the
user cannot access, execvp may return EACCES instead of ENOENT.

fix #1045.
build: ignore generated makefiles on android

gyp currently doesn't support the --generator-output option for android,
this is the best way to ignore generated files for projects using libuv
as a dependency.