Rename SYS_AS_AREA_SHARE_APPROVE and SYS_AS_AREA_SHARE_PERFORM, resp., to
SYS_AS_AREA_ACCEPT and SYS_AS_AREA_SEND, resp. in syscall_t.
Fix prototype of as_area_send() to take only base address of the address
space area as a parameter and read size and flags from the address space
area found at this base address.