Fixes#5151
- Removes `SHARED_VALIDATE` from the enum and turns it into `Map_Shared_Validate :: Map_Flags{.SHARED, .PRIVATE}` so it has the proper value of 0x03.
- Adds `DROPPABLE`.
- Adds constants `MAP_HUGE_SHIFT` and `MAP_HUGE_MASK`.
- Adds the huge page precomputed constants from `mman.h`, defined as the log2 of the size shifted left by `MAP_HUGE_SHIFT`:
Map_Huge_16KB
Map_Huge_64KB
Map_Huge_512KB
Map_Huge_1MB
Map_Huge_2MB
Map_Huge_8MB
Map_Huge_16MB
Map_Huge_32MB
Map_Huge_256MB
Map_Huge_512MB
Map_Huge_1GB
Map_Huge_2GB
Map_Huge_16GB
dec3d6959d