fix formatting for (non-generated) internal source files

- Change formatting standard to Cpp11. Main difference is not having
  the space between two closing >> for nested templates. We don't
  choose c++14, because older versions of clang-format (version 9
  and earlier) don't know this value yet, and it doesn't make a
  difference in the formatting.
- Apply clang-format to all (non generated) internal source files.
- Manually fix some code sections (clang-format on/off) and c-strings
- Exclude some embedded external files with very different formatting
  (gtest/gmock)
- Add script to format all source files

Change-Id: Ic6cea41575ad6e37c9e136dbce176b0d505dc44d

internal/ceres/stringprintf.cc

@@ -62,7 +62,7 @@ void StringAppendV(string* dst, const char* format, va_list ap) {
       return;
     }
 
-#if defined (_MSC_VER)
+#if defined(_MSC_VER)
     // Error or MSVC running out of space.  MSVC 8.0 and higher
     // can be asked about space needed with the special idiom below:
     va_copy(backup_ap, ap);
@@ -78,7 +78,7 @@ void StringAppendV(string* dst, const char* format, va_list ap) {
 
   // Increase the buffer size to the size requested by vsnprintf,
   // plus one for the closing \0.
-  int length = result+1;
+  int length = result + 1;
   char* buf = new char[length];
 
   // Restore the va_list before we use it again
@@ -93,7 +93,6 @@ void StringAppendV(string* dst, const char* format, va_list ap) {
   delete[] buf;
 }
 
-
 string StringPrintf(const char* format, ...) {
   va_list ap;
   va_start(ap, format);