Fixes to C code for ANA support

The C code for ANA support does not build in my Windows environment because:
* No definition for `uint8_t` because of a missing include
* No definition for `asprintf()`, which is a non-standard function that is present on Linux and *BSD, but MinGW does not implement it

This pull request fixes these issues, but is as yet _completely untested_ since I have no experience with ANA data.  But at least my SunPy can install now.