Auto merge of #1946 - JohnTitor:rollup-66245hd, r=JohnTitor

Rollup of 3 pull requests

Successful merges:

 - #1943 (Add definitions for Linux debug related MAGIC)
 - #1944 (Include sendfile64() for Linux)
 - #1945 (Disable libc-test for MIPS64 for now)

Failed merges:

r? `@ghost`