Implement MIPS Comment Generator in the Trace plugin

[archived-c]

Related to #121 , there is no mips comment generator class. At the moment for MIPS binaries, we instead use the EmptyCommentGenerator which is just a placeholder that does nothing. x86, x86_64, and Arm have comment generators that add comments to the instruction trace denoting the value of operands at runtime. This is especially useful for indirect function calls when used in conjunction with the IDA overlay plugin.