This is a fix for PR c++/17132.
If this new argument is set to EVAL_AVOID_SIDE_EFFECTS, then the object's
memory will not be read while picking the best overload match.
gdb/
* eval.c: Update all calls to find_overload_match.
* valarith.c: Likewise.
(value_user_defined_cpp_op, value_user_defined_op): New
argument NOSIDE. Update all callers.
* valops.c (find_overload_match): New argument NOSIDE.
* value.h (find_overload_match): Update signature.
gdb/testsuite
* gdb.cp/pr17132.cc: New file.
* gdb.cp/pr17132.exp: New file.
