Make LLVM command-line tools overwrite their output files without -f.

This is conventional command-line tool behavior. -f now just means
"enable binary output on terminals".

Add a -f option to llvm-extract and llvm-link, for consistency.

Remove F_Force from raw_fd_ostream and enable overwriting and
truncating by default. Introduce an F_Excl flag to permit users to
enable a failure when the file already exists. This flag is
currently unused.

Update Makefiles and documentation accordingly.

llvm-svn: 79990

lib/Bitcode/Writer/BitWriter.cpp

@@ -18,7 +18,7 @@ using namespace llvm;
 int LLVMWriteBitcodeToFile(LLVMModuleRef M, const char *Path) {
   std::string ErrorInfo;
   raw_fd_ostream OS(Path, ErrorInfo,
-                    raw_fd_ostream::F_Force|raw_fd_ostream::F_Binary);
+                    raw_fd_ostream::F_Binary);
   
   if (!ErrorInfo.empty())
     return -1;