Add rules for stdlib, rustls, and stdio

[lucic71]

This mainly adds translation rules for rustls_ffi. I needed to do a few modifications in cpp2rust/ to be able to add translation rules for typedef'ed integers, for example rustls_ffi::rustls_result (typedef uint32_t rustls_result):

• add support in cpp-rule-preprocessor to define rule types as typedef in C and using in C++. rustls.h uses C specific features, hence the source rules must be put in a src.c file. For example in rustls.h uses the following which is valid C but invalid C++:

enum rustls_result { ... }
typedef uint32_t rustls_result; // same name as the enum

• zero-initialize rust enums using the enum default value, not using 0, in getIntegerLiteral, for example: rustls_result r = 0
• install rustls.h into rules/rustls using the cargo installation instead of copy-pasting the vendored rustls.h file. rules/build.rs takes care of this

[nunoplopes]

why is this file needed and what's the origin?

[lucic71]

It's needed to get the C symbols that we translate to rust, similar to brotli: https://github.com/Cpp2Rust/cpp2rust/tree/master/rules/brotli/brotli

This is the origin: https://github.com/rustls/rustls-ffi/blob/main/librustls/src/rustls.h

I installed the deb package (https://github.com/rustls/rustls-ffi/releases/tag/v0.15.3) for rustls-ffi on my system and copied /usr/include/rustls.h into rules/rustls/rustls.h

[lucic71]

I removed the copy-pasted file, see the new description of the PR

[nunoplopes]

this change doesn't look intended

[lucic71]

Yes, that was a mistake. It was asymptomatic because I already had rustls.h generated on my machine