Roll out ASTContext::getTypeSizeInChars(), replacing instances of

"ASTContext::getTypeSize() / 8". Replace [u]int64_t variables with CharUnits
ones as appropriate. 

Also rename RawType, fromRaw(), and getRaw() in CharUnits to QuantityType, 
fromQuantity(), and getQuantity() for clarity.

llvm-svn: 93153