Switch the CharSourceRange array to a small vector. The array was

Switch the CharSourceRange array to a small vector. The array was
a stack array of a magical size with an assert() that we never
overflowed it. That seems incredibly risky. We also have a very nice API
for bundling up a vector we expect to usually have a small size without
loss of functionality or security if the size is excessive.

The fallout is to remove the last pointer+size parameter pair that are
traced through the recursive caret diagnostic emission.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@139217 91177308-0d34-0410-b5e6-96231b3b80d8