Make dbl emit empty strings for non-existent fields

[Andrew Johnson]

The iocsh command
    dbl * "RTYP PREC EGU DTYP DESC"
emits a comma-separated list of quoted field values for the listed fields, but completely ignores the fields that don't exist for a particular record type. The results are difficult to parse; fields that don't exist should at least be given an empty place-holder. They can be distinguished from empty fields by the quotes.

While working on this, also make sure that the output is properly escaped (there's a libCom function for that) so that the output for string fields that contain double-quotes can still be parsed properly.

[Kim, Kukhee (khkim)]

=== modified file 'src/db/dbTest.c'
--- src/db/dbTest.c 2009-07-08 19:08:22 +0000
+++ src/db/dbTest.c 2010-05-25 15:03:35 +0000
@@ -155,6 +155,7 @@
                     if (!strcmp(papfields[ifield], "recordType")) {
                         pvalue = dbGetRecordTypeName(pdbentry);
                     } else {
+ printf(", ");
                         continue;
                     }
                 } else {