Remove redundant `Symtab->`.
Remove redundant `Symtab->`.

`SymbolTable` is a singleton class and is a global variable for the
unique instance, so we can always refer the symtab by `Symtab->`.
However, we don't need to use the global varaible from member functions
of SymbolTable class.

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@344075 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld