Megafunction

The Verilog MegaFuction is instantiating lpm_mult, also multipliers inferred form HDL code do. As most low level libraries, it's coded in AHDL. See lpm_mult.tdf and additional code in multcore.tdf which can be found in quartus\libraries\megafunctions.

There's no Verilog multiplier code. As already mentioned in post# 2, the internal library code (as far written in readable HDL) uses different languages, in this case AHDL.