Rename parser token REF to REF_P to avoid a symbol conflict (babelfis…

…h-for-postgresql#832)

In engine commit 956042f3, REF was redefined as REF_P. This causes a
build error in Babel extensions due to the symbol change.
Update REF to REF_P in order to comply with the engine keywords.

Task: BABEL-OSS
Signed-off by: Kuntal Ghosh kuntalgh@amazon.com

contrib/babelfishpg_tsql/src/backend_parser/kwlist.h

@@ -375,7 +375,7 @@ PG_KEYWORD("real", REAL, COL_NAME_KEYWORD)
 PG_KEYWORD("reassign", REASSIGN, UNRESERVED_KEYWORD)
 PG_KEYWORD("recheck", RECHECK, UNRESERVED_KEYWORD)
 PG_KEYWORD("recursive", RECURSIVE, UNRESERVED_KEYWORD)
-PG_KEYWORD("ref", REF, UNRESERVED_KEYWORD)
+PG_KEYWORD("ref", REF_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("references", REFERENCES, RESERVED_KEYWORD)
 PG_KEYWORD("referencing", REFERENCING, UNRESERVED_KEYWORD)
 PG_KEYWORD("refresh", REFRESH, UNRESERVED_KEYWORD)