pgsql: Rename pg_regress option --multibyte to --encoding

Rename pg_regress option --multibyte to --encoding

Also refactor things a little bit so that the same methods for setting
test locale and encoding can be used everywhere.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/f536d4194293f900577c728bfa4e62075a4c7da0

Modified Files
--------------
contrib/unaccent/Makefile         |    5 +++--
doc/src/sgml/regress.sgml         |    4 ++--
src/Makefile.global.in            |   10 ++++++++--
src/interfaces/ecpg/test/Makefile |   16 +++++-----------
src/test/regress/GNUmakefile      |    8 +-------
src/test/regress/pg_regress.c     |    6 +++---
src/tools/msvc/vcregress.pl       |    6 +++---
7 files changed, 25 insertions(+), 30 deletions(-)