Update btree_gist extension for parallel query

All functions provided by this extension are PARALLEL SAFE.

Discussion: https://postgr.es/m/AM5PR0901MB1587E47B1ACF23C6089DFCA3FD9B0%40AM5PR0901MB1587.eurprd09.prod.outlook.com
Author: Steven Winfield

contrib/btree_gist/Makefile

@@ -31,7 +31,8 @@ OBJS =  \
 EXTENSION = btree_gist
 DATA = btree_gist--1.0--1.1.sql \
        btree_gist--1.1--1.2.sql btree_gist--1.2.sql btree_gist--1.2--1.3.sql \
-       btree_gist--1.3--1.4.sql btree_gist--1.4--1.5.sql
+       btree_gist--1.3--1.4.sql btree_gist--1.4--1.5.sql \
+       btree_gist--1.5--1.6.sql
 PGFILEDESC = "btree_gist - B-tree equivalent GiST operator classes"
 
 REGRESS = init int2 int4 int8 float4 float8 cash oid timestamp timestamptz \

contrib/btree_gist/btree_gist.control

 # btree_gist extension
 comment = 'support for indexing common datatypes in GiST'
-default_version = '1.5'
+default_version = '1.6'
 module_pathname = '$libdir/btree_gist'
 relocatable = true
 trusted = true