Fix ld warnings for loongarch64
I figure out the cause is Fedora 26 changed default openssl to version 1.1.0 and...
STAF 3.4.26 failed to build on Fedora 26
Check fallocate function first
Fix build with GCC 6
Make sure nbd-client child exits if parent exited
Deal with end of line
Properly get the declarations of pread/pwrite