Fix typos

Tiger Language Reference Manual / Semantics / Expressions

• > Since every class itnherits from Object, you will always find a common root. Should be inherits

Compiler Stages / TC-2 / Code to Write

• > Complete actions to instantiate AST nodes with the driver’s methods accessible using td.tp_. Should be tp.td_

Compiler Stages / TC-7 / Code to Write / Codegen

• > src/target/mips/mips-matcher.cc -> src/target/mips/spim-matcher.cc

Source Code / Project Layout / Lib Misc

• > lambda-viitor.* -> lambda-visitor.*