Remove many superfluous SmallString::str() calls.

Now that SmallString is a first-class citizen, most SmallString::str()
calls are not required. This patch removes a whole bunch of them, yet
there are lots more.

There are two use cases where str() is really needed:
1) To use one of StringRef member functions which is not available in
SmallString.
2) To convert to std::string, as StringRef implicitly converts while 
SmallString do not. We may wish to change this, but it may introduce
ambiguity.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232622 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/APInt.cpp

@@ -2297,7 +2297,7 @@ void APInt::dump() const {
 void APInt::print(raw_ostream &OS, bool isSigned) const {
   SmallString<40> S;
   this->toString(S, 10, isSigned, /* formatAsCLiteral = */false);
-  OS << S.str();
+  OS << S;
 }
 
 // This implements a variety of operations on a representation of