caput should warn when truncating value string

When the caput program is asked to put a string to a PV using the type DBR_STRING, it should print a warning (something like "string value truncated") if the string value will not fit into the 40 characters available after escaping. New users might think that the truncation just occurs for display purposes. Currently:

tux% caput anj:exit.DESC "This is a string which is much longer than the 40 characters available"
Old : anj:exit.DESC Exit subroutine
New : anj:exit.DESC This is a string which is much longer t