sheep/http: change type of 'req->data_length' to uint64_t

Change the type of 'data_length' in 'struct http_request' so we can
receive http request larger than 4G in 32bit environment.

Signed-off-by: Robin Dong <sanbai@taobao.com>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>
sheep: fix format of printf for uint64_t

Previously, we use '%lu' to printf uint64_t argument, that is incorrect especially
int 32bit machines. So change it to '%PRIu64'.

Signed-off-by: Robin Dong <sanbai@taobao.com>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>
sheep: add set_bit_64() for uint64_t type

When building sheepdog in 32bit machie, the gcc report:

	object_cache.c: In function ‘calc_object_bmap’:
	object_cache.c:146:3: warning: passing argument 2 of ‘set_bit’ from incompatible pointer type [enabled by default]
	../include/bitops.h:133:20: note: expected ‘long unsigned int *’ but argument is of type ‘uint64_t *’
	object_cache.c: In function ‘push_cache_object’:
	object_cache.c:475:16: warning: comparison of distinct pointer types lacks a cast [enabled by default]

because 'long unsigned int' is different to 'uint64_t' in 32bit environment. So we
add a new function set_bit_64() for uint64_t argument.

Signed-off-by: Robin Dong <sanbai@taobao.com>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>
sheep: fix warning of compiler for shadow argument

The compiler report:

	http/kv.c: In function ‘vdi_read_write’:
	http/kv.c:633: warning: declaration of ‘read’ shadows a global declaration
	/usr/include/unistd.h:357: warning: shadowed declaration is here
	http/kv.c: In function ‘http_time’:
	http/kv.c:1139: warning: declaration of ‘time’ shadows a global declaration
	/usr/include/time.h:186: warning: shadowed declaration is here

when compiling sheepdog. So we shoud change the name of argument to fix it.

Signed-off-by: Robin Dong <sanbai@taobao.com>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>