Backpatch: Fix tsvector_out() and tsquery_out() to escape backslesh, add test of that.

Patch by Bruce Momjian <bruce@momjian.us>

contrib/tsearch2/expected/tsearch2.out

@@ -331,6 +331,12 @@ SELECT '''the wether'':dc & '' sKies '':BC & a:d b:a';
  'the wether':dc & ' sKies ':BC & a:d b:a
 (1 row)
 
+SELECT tsvector_in(tsvector_out($$'\\as' ab\c ab\\c AB\\\c ab\\\\c$$::tsvector)), tsquery_in(tsquery_out($$'\\as'$$::tsquery));
+              tsvector_in               | tsquery_in 
+----------------------------------------+------------
+ '\\as' 'abc' 'AB\\c' 'ab\\c' 'ab\\\\c' | '\\as'
+(1 row)
+
 select 'a' < 'b & c'::tsquery;
  ?column? 
 ----------

contrib/tsearch2/query.c

@@ -765,6 +765,11 @@ infix(INFIX * in, bool first)
 				*(in->cur) = '\'';
 				in->cur++;
 			}
+			else if (t_iseq(op, '\\'))
+			{
+				*(in->cur) = '\\';
+				in->cur++;
+			}
 			COPYCHAR(in->cur, op);
 
 			clen = pg_mblen(op);

contrib/tsearch2/sql/tsearch2.sql

@@ -67,6 +67,8 @@ SELECT '1&(2&(4&(5|!6)))'::tsquery;
 SELECT E'1&(''2''&('' 4''&(\\|5 | ''6 \\'' !|&'')))'::tsquery;
 SELECT '''the wether'':dc & '' sKies '':BC & a:d b:a';
 
+SELECT tsvector_in(tsvector_out($$'\\as' ab\c ab\\c AB\\\c ab\\\\c$$::tsvector)), tsquery_in(tsquery_out($$'\\as'$$::tsquery));
+
 select 'a' < 'b & c'::tsquery;
 select 'a' > 'b & c'::tsquery;
 select 'a | f' < 'b & c'::tsquery;

contrib/tsearch2/tsvector.c

@@ -550,6 +550,14 @@ tsvector_out(PG_FUNCTION_ARGS)
 				curout = outbuf + pos;
 				*curout++ = '\'';
 			}
+			else if (t_iseq(curin, '\\'))
+			{
+				int4		pos = curout - outbuf;
+
+				outbuf = (char *) repalloc((void *) outbuf, ++lenbuf);
+				curout = outbuf + pos;
+				*curout++ = '\\';
+			}
 			while (len--)
 				*curout++ = *curin++;
 		}