Small fixes and improvements

This commit fixes a couple issues and lightly improves some features over the various Dynamatic tools. Changes are described below.

Buffers: add missing header for modern compiler versions
HlsVerifier: add missing header for modern compiler versions and modifies Modelsim script to dump waveform resulting from testbench execution
arithmetic_units: fix incorrect trunc_op architecture
elastic_components: generalize control merge architecture to work with arbitrary number of inputs
dot2vhdl: generalize to work for control merges with arbitrary number of inputs

lana555 / dynamatic