Fix CLI error handling and build metadata

[mrzetti]

• src/main.cpp: return main_inner() from main(), so parse/open errors exit nonzero.
• src/main.cpp: added missing failure returns for invalid --client and --server.
• src/main.cpp: added explicit return 0 at the end of main_inner().
• src/gpu.cu: wrapped cudaFuncSetAttribute(...) in TRY_CUDA; (CUDA docs confirm it returns cudaError_t).
• makefile: added missing source/header dependencies for libcubiomes.a and gpu.o.
• .gitignore: added main and main.exe, since the documented build creates main.

Verification

• make
• ./main --definitely-invalid
• ./main --client invalid-address
• ./main --server invalid-address

[mrzetti]

build will succeed after #1 is merged

[BoySanic]

Overall, I think you're formatting a bunch of stuff needlessly (it doesn't even seem to change indentation or anything - maybe line endings?).

I'd like to see this revised so that only the lines you're actually changing are being changed, and not the surrounding lines.