Remove/fix some unused variable compile problems.
Put function zcrypt_keychain_find() inside a ifdef _KERNEL because it's not used.
Disable the ASSERT3U() using SPA_VERSION_CRYPTO until the latter can be defined.
Fix missing () between && within || to fix compile errors
when compiling under --debug.
Put some unused function between ifdef _KERNEL.
Fix 'unused variable' compile errors.
If AT_{UID,GID} is already defined (which they should be), undefine them. They will be defined properly later in the include chain.
Fixa a compile error: 'name' may be used uninitialized in this function