smarter summary strings:

 - formats %s %char[] %c and %a now work to print 0-terminated c-strings if they are applied to a char* or char[] even without the [] operator (e.g. ${var%s})
 - array formats (char[], intN[], ..) now work when applied to an array of a scalar type even without the [] operator (e.g. ${var%int32_t[]})
LLDB will not crash because of endless loop when trying to obtain a summary for an object that has no value and references itself in its summary string
In many cases, a wrong summary string will now display an "<error>" message instead of giving out an empty string

llvm-svn: 135007