Add DBMS_OUTPUT package in ivorysql_ora extension

Implement Oracle-compatible DBMS_OUTPUT package providing:
- PUT_LINE, PUT, NEW_LINE for buffered output
- GET_LINE, GET_LINES for retrieving output
- ENABLE/DISABLE for buffer control
- Buffer overflow detection (ORU-10027)

Located in contrib/ivorysql_ora/src/builtin_packages/dbms_output/
following IvorySQL maintainer guidance (discussion IvorySQL#988).

Includes design documentation and Oracle compatibility comparison
with 82% test compatibility rate (27/33 tests pass).

Known differences from Oracle:
- NULL stored as empty string vs NULL
- Re-ENABLE clears buffer vs preserves
- Buffer size range 2000-1000000 (Oracle: 2000-unlimited)
- No 32767 byte line length limit

Author: rophy

contrib/ivorysql_ora/Makefile

@@ -25,6 +25,7 @@ OBJS = \
 	src/builtin_functions/datetime_datatype_functions.o \
 	src/builtin_functions/numeric_datatype_functions.o \
 	src/builtin_functions/misc_functions.o \
+	src/builtin_packages/dbms_output/dbms_output.o \
 	src/merge/ora_merge.o \
 	src/sysview/sysview_functions.o \
 	src/xml_functions/ora_xml_functions.o
@@ -69,7 +70,8 @@ ORA_REGRESS = \
 	datatype_and_func_bugs \
 	ora_sysview \
 	ora_like_operator \
-	ora_xml_functions
+	ora_xml_functions \
+	ora_dbms_output
 
 SHLIB_LINK += -lxml2