[ORC] Rename VSO to JITDylib.

VSO was a little close to VDSO (an acronym on Linux for Virtual Dynamic Shared
Object) for comfort. It also risks giving the impression that instances of this
class could be shared between ExecutionSessions, which they can not.

JITDylib seems moderately less confusing, while still hinting at how this
class is intended to be used, i.e. as a JIT-compiled stand-in for a dynamic
library (code that would have been a dynamic library if you had wanted to
compile it ahead of time).

llvm-svn: 340084
diff --git a/llvm/unittests/ExecutionEngine/Orc/LegacyAPIInteropTest.cpp b/llvm/unittests/ExecutionEngine/Orc/LegacyAPIInteropTest.cpp
index 746ae1d..05fe921 100644
--- a/llvm/unittests/ExecutionEngine/Orc/LegacyAPIInteropTest.cpp
+++ b/llvm/unittests/ExecutionEngine/Orc/LegacyAPIInteropTest.cpp
@@ -19,12 +19,12 @@
 namespace {
 
 TEST_F(LegacyAPIsStandardTest, TestLambdaSymbolResolver) {
-  cantFail(V.define(absoluteSymbols({{Foo, FooSym}, {Bar, BarSym}})));
+  cantFail(JD.define(absoluteSymbols({{Foo, FooSym}, {Bar, BarSym}})));
 
   auto Resolver = createSymbolResolver(
-      [&](const SymbolNameSet &Symbols) { return V.lookupFlags(Symbols); },
+      [&](const SymbolNameSet &Symbols) { return JD.lookupFlags(Symbols); },
       [&](std::shared_ptr<AsynchronousSymbolQuery> Q, SymbolNameSet Symbols) {
-        return V.legacyLookup(std::move(Q), Symbols);
+        return JD.legacyLookup(std::move(Q), Symbols);
       });
 
   SymbolNameSet Symbols({Foo, Bar, Baz});
@@ -66,22 +66,22 @@
   EXPECT_TRUE(OnResolvedRun) << "OnResolved was never run";
 }
 
-TEST(LegacyAPIInteropTest, QueryAgainstVSO) {
+TEST(LegacyAPIInteropTest, QueryAgainstJITDylib) {
 
   ExecutionSession ES(std::make_shared<SymbolStringPool>());
   auto Foo = ES.getSymbolStringPool().intern("foo");
 
-  auto &V = ES.createVSO("V");
+  auto &JD = ES.createJITDylib("JD");
   JITEvaluatedSymbol FooSym(0xdeadbeef, JITSymbolFlags::Exported);
-  cantFail(V.define(absoluteSymbols({{Foo, FooSym}})));
+  cantFail(JD.define(absoluteSymbols({{Foo, FooSym}})));
 
   auto LookupFlags = [&](const SymbolNameSet &Names) {
-    return V.lookupFlags(Names);
+    return JD.lookupFlags(Names);
   };
 
   auto Lookup = [&](std::shared_ptr<AsynchronousSymbolQuery> Query,
                     SymbolNameSet Symbols) {
-    return V.legacyLookup(std::move(Query), Symbols);
+    return JD.legacyLookup(std::move(Query), Symbols);
   };
 
   auto UnderlyingResolver =