[Logging] Replace Log::Printf with LLDB_LOG macro (NFC)

This patch replaces explicit calls to log::Printf with the new LLDB_LOGF
macro. The macro is similar to LLDB_LOG but supports printf-style format
strings, instead of formatv-style format strings.

So instead of writing:

  if (log)
    log->Printf("%s\n", str);

You'd write:

  LLDB_LOG(log, "%s\n", str);

This change was done mechanically with the command below. I replaced the
spurious if-checks with vim, since I know how to do multi-line
replacements with it.

  find . -type f -name '*.cpp' -exec \
  sed -i '' -E 's/log->Printf\(/LLDB_LOGF\(log, /g' "{}" +

Differential revision: https://reviews.llvm.org/D65128

llvm-svn: 366936
diff --git a/lldb/source/Symbol/ClangASTContext.cpp b/lldb/source/Symbol/ClangASTContext.cpp
index 2055233..b348ba7 100644
--- a/lldb/source/Symbol/ClangASTContext.cpp
+++ b/lldb/source/Symbol/ClangASTContext.cpp
@@ -956,7 +956,7 @@
       llvm::SmallVector<char, 32> diag_str(10);
       info.FormatDiagnostic(diag_str);
       diag_str.push_back('\0');
-      m_log->Printf("Compiler diagnostic: %s\n", diag_str.data());
+      LLDB_LOGF(m_log, "Compiler diagnostic: %s\n", diag_str.data());
     }
   }