MFC r319048,r319049,r319051,r319054:

r319048:

Push snapshot_file copying down into run_tests function, and mark snapshot_file
const char *.

This fixes a bogus set of errors from gcc about strdup not being allowed a NULL
argument.

r319049:

Bump WARNS from 1 to 3 after recent commits to fix warnings in the
directory.

Tested with: clang 4.0, gcc 4.2.1, gcc 6.3.0

r319051:

hostent_test_getnameinfo_eq(..): initialize found_a_host to false

CID: 1368943

r319054:

hostent_test_getaddrinfo_eq(..): call freeaddrinfo on ai when done

This plugs a leak of memory allocated via getaddrinfo.

CID: 1346866