Implement support for C++

[Phantomical]

This involves adding support for some missing instructions along with several builtin functions.

To find out try running a C++ program, seeing what crashes, and list it here.

• Remove pthread dependencies from libc #491
• Implement libunwind functionality in caffeine #492
• Caffeine should be calling global ctors on startup #631
• Implement LLVM variable length argument intrinsics #593