Rename `Symtab` private memory to avoid confusion with global `Symtab`

This is also consistent with SymVector that exists in COFF port
and soon to be added to the wasm port.

Split off as part of https://reviews.llvm.org/D40371

Differential Revision: https://reviews.llvm.org/D40525

llvm-svn: 319113
diff --git a/lld/wasm/SymbolTable.cpp b/lld/wasm/SymbolTable.cpp
index 97670cf..722d5a0 100644
--- a/lld/wasm/SymbolTable.cpp
+++ b/lld/wasm/SymbolTable.cpp
@@ -34,7 +34,7 @@
 
 void SymbolTable::reportRemainingUndefines() {
   std::unordered_set<Symbol *> Undefs;
-  for (auto &I : Symtab) {
+  for (auto &I : SymMap) {
     Symbol *Sym = I.second;
     if (Sym->isUndefined() && !Sym->isWeak() &&
         Config->AllowUndefinedSymbols.count(Sym->getName()) == 0) {
@@ -56,14 +56,14 @@
 }
 
 Symbol *SymbolTable::find(StringRef Name) {
-  auto It = Symtab.find(CachedHashStringRef(Name));
-  if (It == Symtab.end())
+  auto It = SymMap.find(CachedHashStringRef(Name));
+  if (It == SymMap.end())
     return nullptr;
   return It->second;
 }
 
 std::pair<Symbol *, bool> SymbolTable::insert(StringRef Name) {
-  Symbol *&Sym = Symtab[CachedHashStringRef(Name)];
+  Symbol *&Sym = SymMap[CachedHashStringRef(Name)];
   if (Sym)
     return {Sym, false};
   Sym = make<Symbol>(Name, false);