3.0: Remove 'sanity check' and 'struct IDs'

These functions have not been widely used or maintained. Their purpose was to assist applications in verifying the structure sizes used by the library conformed to that of what their application was expecting. However in reality the structure sizes rarely changed, and when they did change, they only changed in compatible ways so that applications compiled against older versions would never break anyway.

Applications using newer versions of the structures would also never work anyway since the library itself would reject the newer versions at runtime.