net: declare lib_getaddrinfo as returning int32

    
    Otherwise on a 64-bit system we will read the 32-bit value as a 64-bit
    value.  Since getaddrinfo returns negative numbers as error values,
    these will be interpreted as numbers like 0xfffffffe rather than -2,
    and the comparisons with values like syscall.EAI_NONAME will fail.
    
    Fixes golang/go#23645
    
    Reviewed-on: https://go-review.googlesource.com/91296

From-SVN: r257299

gcc/go/gofrontend/MERGE

-71758f9ca1804743afe178f0e2fca489e0217474
+b833695618d1a5d9d531f5ba0f9c07c7e35e0073
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/net/cgo_unix.go

@@ -23,7 +23,7 @@ import (
 )
 
 //extern getaddrinfo
-func libc_getaddrinfo(node *byte, service *byte, hints *syscall.Addrinfo, res **syscall.Addrinfo) int
+func libc_getaddrinfo(node *byte, service *byte, hints *syscall.Addrinfo, res **syscall.Addrinfo) int32
 
 //extern freeaddrinfo
 func libc_freeaddrinfo(res *syscall.Addrinfo)