Change isc_buffer_reallocate() into a static functions as it is not used...

Change isc_buffer_reallocate() into a static functions as it is not used outside of isc_buffer_reserve()

(cherry picked from commit 20faf465)
13 jobs for 443-isc_buffer_printf-fixes-v9_12 in 9 minutes and 25 seconds (queued for 7 seconds)
Status Job ID Name Coverage
  Precheck
passed precheck:debian:sid:amd64 #29575
amd64 docker linux

00:00:12

 
  Build
passed build:centos:centos6:amd64 #29576
amd64 docker linux

00:02:14

passed build:centos:centos7:amd64 #29577
amd64 docker linux

00:02:20

passed build:debian:sid:amd64 #29578
amd64 docker linux

00:02:54

passed build:debian:sid:i386 #29579
i386 docker linux

00:03:07

 
  Test
passed systemtest:centos:centos6:amd64 #29584
amd64 docker linux

00:05:10

passed systemtest:centos:centos7:amd64 #29585
amd64 docker linux

00:05:17

passed systemtest:debian:sid:amd64 #29586
amd64 docker linux

00:05:19

passed systemtest:debian:sid:i386 #29587
i386 docker linux

00:05:09

passed unittest:centos:centos6:amd64 #29580
amd64 docker linux

00:01:03

passed unittest:centos:centos7:amd64 #29581
amd64 docker linux

00:01:03

passed unittest:debian:sid:amd64 #29582
amd64 docker linux

00:00:56

passed unittest:debian:sid:i386 #29583
i386 docker linux

00:00:54