pgsql: Rename ecpg's various "extern.h" files to have distinct names.

Rename ecpg's various "extern.h" files to have distinct names.

This should reduce confusion, and in particular make it safe to
copy typename.c into preproc/ and compile it there.

This doesn't affect anything outside ecpg, and particularly not
end users, because these files don't get installed; they just
exist to share declarations among the .c files of each subdirectory.

Discussion: https://postgr.es/m/31364.1543511708@sss.pgh.pa.us

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/3295f82022ff0da95c96d8ca763e1d8902345466

Modified Files
--------------
src/interfaces/ecpg/ecpglib/connect.c | 2 +-
src/interfaces/ecpg/ecpglib/data.c | 2 +-
src/interfaces/ecpg/ecpglib/descriptor.c | 2 +-
src/interfaces/ecpg/ecpglib/{extern.h => ecpglib_extern.h} | 8 ++++----
src/interfaces/ecpg/ecpglib/error.c | 2 +-
src/interfaces/ecpg/ecpglib/execute.c | 2 +-
src/interfaces/ecpg/ecpglib/memory.c | 2 +-
src/interfaces/ecpg/ecpglib/misc.c | 2 +-
src/interfaces/ecpg/ecpglib/prepare.c | 2 +-
src/interfaces/ecpg/ecpglib/sqlda.c | 2 +-
src/interfaces/ecpg/ecpglib/typename.c | 2 +-
src/interfaces/ecpg/pgtypeslib/common.c | 2 +-
src/interfaces/ecpg/pgtypeslib/datetime.c | 2 +-
src/interfaces/ecpg/pgtypeslib/dt_common.c | 2 +-
src/interfaces/ecpg/pgtypeslib/interval.c | 2 +-
src/interfaces/ecpg/pgtypeslib/numeric.c | 2 +-
src/interfaces/ecpg/pgtypeslib/{extern.h => pgtypeslib_extern.h} | 8 ++++----
src/interfaces/ecpg/pgtypeslib/timestamp.c | 2 +-
src/interfaces/ecpg/preproc/c_keywords.c | 2 +-
src/interfaces/ecpg/preproc/descriptor.c | 2 +-
src/interfaces/ecpg/preproc/ecpg.c | 2 +-
src/interfaces/ecpg/preproc/ecpg.header | 2 +-
src/interfaces/ecpg/preproc/ecpg_keywords.c | 2 +-
src/interfaces/ecpg/preproc/keywords.c | 2 +-
src/interfaces/ecpg/preproc/output.c | 2 +-
src/interfaces/ecpg/preproc/parser.c | 2 +-
src/interfaces/ecpg/preproc/pgc.l | 2 +-
src/interfaces/ecpg/preproc/{extern.h => preproc_extern.h} | 3 +--
src/interfaces/ecpg/preproc/type.c | 2 +-
src/interfaces/ecpg/preproc/variable.c | 2 +-
30 files changed, 36 insertions(+), 37 deletions(-)