Remove contrib/tsearch2.

This module was intended to ease migrations of applications that used
the pre-8.3 version of text search to the in-core version introduced
in that release.  However, since all pre-8.3 releases of the database
have been out of support for more than 5 years at this point, we
expect that few people are depending on it at this point.  If some
people still need it, nothing prevents it from being maintained as a
separate extension, outside of core.

Discussion: http://postgr.es/m/CA+Tgmob5R8aDHiFRTQsSJbT1oreKg2FOSBrC=2f4tqEH3dOMAg@mail.gmail.com

src/test/modules/test_parser/test_parser.c

@@ -28,7 +28,6 @@ typedef struct
 	int			pos;			/* position of the parser */
 } ParserState;
 
-/* copy-paste from wparser.h of tsearch2 */
 typedef struct
 {
 	int			lexid;

src/tools/msvc/Mkvcbuild.pm

@@ -36,7 +36,7 @@ my @contrib_uselibpgport   = ('oid2name', 'pg_standby', 'vacuumlo');
 my @contrib_uselibpgcommon = ('oid2name', 'pg_standby', 'vacuumlo');
 my $contrib_extralibs      = undef;
 my $contrib_extraincludes =
-  { 'tsearch2' => ['contrib/tsearch2'], 'dblink' => ['src/backend'] };
+  { 'dblink' => ['src/backend'] };
 my $contrib_extrasource = {
 	'cube' => [ 'contrib/cube/cubescan.l', 'contrib/cube/cubeparse.y' ],
 	'seg'  => [ 'contrib/seg/segscan.l',   'contrib/seg/segparse.y' ], };