Add VeriFast kernel queue proofs (#117)

FreeRTOS/Test/VeriFast/scripts/diff_files.md

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+# Generate diffs between FreeRTOS source and proofs
+
+## Requirements
+
+  - python3
+  - ctags 5.8
+  - diff 3.4+
+  - [diff2html](https://diff2html.xyz/)
+
+## Instructions
+
+The following will extract per-function files from the original FreeRTOS source
+implementation and the proof directory.
+
+
+```
+cd scripts
+./generate_diff_files.sh
+# will extract to ./FreeRTOS-Kernel/generated and ./queue/generated
+```
+
+Then use `diff` for a side-by-side comparison.  Note that the `--color=always`
+flag needs v3.4+:
+
+```
+diff --color=always --width=$COLUMNS --suppress-common-lines --side-by-side FreeRTOS-Kernel/generated queue/generated | less -r
+```
+
+Or generate a html report using `diff2html`:
+
+```
+diff -u FreeRTOS-Kernel/generated queue/generated | diff2html -i stdin
+```
+
+The expectation is that the proofs make minimal changes to the original source
+implementation in the form of:
+
+  - VeriFast annotations `/*@...@*/` and `//*...`
+  - Additional comments explaining the proof `/*...*/`
+  - Flagged changes within `#if[n]def VERIFAST`