Refactor StructCapUser{Header,Data} and StructLinger for API review

 * renamed StructCapUserData to StructUserCapData
 * renamed StructCapUserHeader to StructUserCapHeader
 * made StructLinger public (removed from SystemApi)

Bug: 183513856
Test: m droid
Test: atest libcore.libcore.io.BlockGuardOsTest
Change-Id: I3989c30f9173f62ac3d7b59f407cd3f044cc9404
14 files changed