Blackwell and PDL performance increase

In three linesLlama.cpp adds Programmatic Dependent Launch (PDL) support for Nvidia Blackwell GPUs (CC >= 90). PDL improves kernel execution: +5-6% token generation speedup on Qwen 35B and Gemma 26B, no pre-fill gains. Enable with '-D GGML_CUDA_PDL=ON' at build time.

Summary generated by Claude — human-verified