Port glibc's strstr to Rust

[mre]

What?

https://sourceware.org/git/?p=glibc.git;a=blob;f=string/strstr.c;hb=9d13fb2413921c713f83efe331e8e4d219c62c6b#l21

Why?

My assumption is, that there is a lot of undefined behavior in this code.
We could talk about fuzzing, porting C code, performance benchmarks and more.

How?

• Create a naive implementation of strstr in Rust.
• Benchmark it against the existing C version.
• Port the C strstr version verbatim to Rust.
• Run afl (fuzzing) against it to check for edge-cases.

Thanks for the inspiration @jorgelbg.