pgsql: Move vacuumlazy.c into access/heap.

Move vacuumlazy.c into access/heap.

It's heap table storage specific code that can't realistically be
generalized into table AM agnostic code.

Author: Andres Freund
Discussion: https://postgr.es/m/20180703070645.wchpu5muyto5n647@alap3.anarazel.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/285d8e12055f27bce5675e93fef365b6c337f2b3

Modified Files
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src/backend/access/heap/Makefile                   | 3 ++-
src/backend/{commands => access/heap}/vacuumlazy.c | 6 +++---
src/backend/commands/Makefile                      | 2 +-
src/backend/commands/vacuum.c                      | 2 +-
src/include/access/heapam.h                        | 4 ++++
src/include/commands/vacuum.h                      | 4 ----
6 files changed, 11 insertions(+), 10 deletions(-)