dbStatic: fix CONSTANT links

constantStr==NULL and constantStr=="" have different
meanings for recGblInitConstantLink() which is used with DOL.
constantStr should remain NULL unless explicitly set
by either initial("") or field(..., "")

src/ioc/dbStatic/dbStaticLib.c

@@ -1915,7 +1915,8 @@ long dbInitRecordLinks(dbRecordType *rtyp, struct dbCommon *prec)
             plink->type = CONSTANT;
 
         switch (plink->type) {
-        case CONSTANT: plink->value.constantStr = callocMustSucceed(1, 1, "init CONSTANT link"); break;
+        /* constantStr is allowed to remain NULL if plink->text==NULL */
+        case CONSTANT: plink->value.constantStr = NULL; break;
         case PV_LINK:  plink->value.pv_link.pvname = callocMustSucceed(1, 1, "init PV_LINK"); break;
         case VME_IO: plink->value.vmeio.parm = pNullString; break;
         case CAMAC_IO: plink->value.camacio.parm = pNullString; break;

src/ioc/dbStatic/dbStaticRun.c

@@ -270,9 +270,9 @@ long dbAllocRecord(DBENTRY *pdbentry,const char *precordName)
 
 		plink->type = CONSTANT;
 		if(pflddes->initial) {
-		    plink->value.constantStr =
+		    plink->text =
 			dbCalloc(strlen(pflddes->initial)+1,sizeof(char));
-		    strcpy(plink->value.constantStr,pflddes->initial);
+		    strcpy(plink->text,pflddes->initial);
 		}
 	    }
 	    break;