pgsql: Split Makefile symbol CFLAGS_VECTOR into two symbols.

Split Makefile symbol CFLAGS_VECTOR into two symbols.

Replace CFLAGS_VECTOR with CFLAGS_UNROLL_LOOPS and CFLAGS_VECTORIZE,
allowing us to distinguish whether we want to apply -funroll-loops,
-ftree-vectorize, or both to a particular source file. Up to now
the only consumer of the symbol has been checksum.c which wants
both, so that there was no need to distinguish; but that's about
to change.

Amit Khandekar, reviewed and edited a little by me

Discussion: /messages/by-id/CAJ3gD9evtA_vBo+WMYMyT-u=keHX7-r8p2w7OSRfXf42LTwCZQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/695de5d1eda6382b20fadb0a2b2d286b57a6a61c

Modified Files
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configure | 32 +++++++++++++++++++-------------
configure.ac | 17 +++++++++++------
src/Makefile.global.in | 3 ++-
src/backend/storage/page/Makefile | 4 ++--
4 files changed, 34 insertions(+), 22 deletions(-)