Add handling for custom partition table offsets #216

Job	Run time
Check lib (x86_64-unknown-linux-gnu)	45s
Clippy (x86_64-unknown-linux-gnu)	54s
Check lib (aarch64-unknown-linux-gnu)	1m 43s
Check MSRV (x86_64-unknown-linux-gnu)	30s
Clippy (aarch64-unknown-linux-gnu)	1m 50s
Check (x86_64-apple-darwin)	58s
Check lib (armv7-unknown-linux-gnueabihf)	1m 14s
Clippy (armv7-unknown-linux-gnueabihf)	1m 41s
Check (x86_64-unknown-linux-gnu)	29s
Check MSRV (aarch64-unknown-linux-gnu)	1m 56s
Check (x86_64-unknown-linux-musl)	31s
Check MSRV (armv7-unknown-linux-gnueabihf)	1m 59s
Rustfmt	20s
Check (x86_64-pc-windows-msvc)	2m 17s
Unit Tests (x86_64-unknown-linux-gnu)	37s
Check (aarch64-unknown-linux-gnu)	1m 35s
Unit Tests (aarch64-unknown-linux-gnu)	1m 18s
Check (armv7-unknown-linux-gnueabihf)	1m 32s
Unit Tests (armv7-unknown-linux-gnueabihf)	1m 16s
	23m 25s

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