pgsql: Fix inclusions of postgres_fe.h from .h files.

Fix inclusions of postgres_fe.h from .h files.

We have a project policy that every .c file should start by including
postgres.h, postgres_fe.h, or c.h as appropriate; and then there is no
need for any .h file to explicitly include any of these. Fix a few
headers that were violating this policy by including postgres_fe.h.

Discussion: https://postgr.es/m/CAEepm=2zCoeq3QxVwhS5DFeUh=yU6z81pbWMgfOB8OzyiBwxzw@mail.gmail.com
Discussion: https://postgr.es/m/11634.1488932128@sss.pgh.pa.us

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/9722bb5757c5e90617be685bf127911b63efe08d

Modified Files
--------------
src/interfaces/ecpg/ecpglib/extern.h | 2 +-
src/interfaces/ecpg/test/pg_regress_ecpg.c | 3 +++
src/interfaces/libpq/libpq-int.h | 1 -
src/test/isolation/isolation_main.c | 2 ++
src/test/regress/pg_regress.c | 4 +++-
src/test/regress/pg_regress.h | 1 -
src/test/regress/pg_regress_main.c | 2 ++
7 files changed, 11 insertions(+), 4 deletions(-)