Enabled body buffer shared memory segmentation.

Changeset #699 fixes shared memory allocation: continous buffer with
requested size should be allocated or function failed.  For body longer
than 10 Mb, this allocation will definitely fails.

For body buffer it is not required to send it in a single continous buffer,
so, need to request minimum reasonable amount of shared memory and try to
extend it, if possible or allocate next buffer.

src/nxt_port_memory_int.h

@@ -89,7 +89,7 @@ struct nxt_port_mmap_tracking_msg_s {
     nxt_chunk_id_t      tracking_id;   /* Tracking index. */
 };
 
-static nxt_bool_t
+nxt_inline nxt_bool_t
 nxt_port_mmap_get_free_chunk(nxt_free_map_t *m, nxt_chunk_id_t *c);
 
 #define nxt_port_mmap_get_chunk_busy(m, c)                                    \
@@ -126,7 +126,7 @@ nxt_port_mmap_chunk_start(nxt_port_mmap_header_t *hdr, nxt_chunk_id_t c)
 }
 
 
-static nxt_bool_t
+nxt_inline nxt_bool_t
 nxt_port_mmap_get_free_chunk(nxt_free_map_t *m, nxt_chunk_id_t *c)
 {
     const nxt_free_map_t  default_mask = (nxt_free_map_t) -1;