[GCC 11] On entry cache cleanups

[Andrew MacLeod]

The following \3 patches were applied to releases/gcc-11.  They form the 
bulk of the on-entry fixes in trunk

d3344fbe7bc25f414671ad7a37d2e9601942597d
Clean up and virtualize the on-entry cache interface.  cherry picked 
from 14b0f37a644d7b59e1737fb275ec4fff044972a8

4ed9f2e65a69e270ea47221318d64ace3d50848
Implement multi-bit aligned accessors for sparse bitmap. cherry picked 
from commit 5ad089a3c946aec655436fa3b0b50d6574b78197

52f0aa4dee8401ef3958dbf789780b0ee877beab
Implement a sparse bitmap representation for Rangers on-entry cache. 
cherry picked from commit 9858cd1a6827ee7a928318acb5e86389f79b4012

Bootstrapped on x86_64-pc-linux-gnu with no regressions.  pushed.

Andrew