Non-standard libc headers

[ludfjig]

For example, hyperlight-guest has "printf.h", but usually the printf-type functions are defined in "stdio.h". This makes it harder to port existing programs to run with hyperlight's libc, as it requires more manual patching of code. We should aim to make it as frictionless as possible to run existing code inside hyperlight, and one way we can do this is aim to have more standard libc header files