pgsql: Remove ancient downcasing code from procedural language operatio

Remove ancient downcasing code from procedural language operations.

A very long time ago, language names were specified as literals rather
than identifiers, so this code was added to do case-folding. But that
style has ben deprecated for many years so this isn't needed any more.
Language names will still be downcased when specified as unquoted
identifiers, but quoted identifiers or the old style using string
literals will be left as-is.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/67dc4eed42186ba6a2456578899bfd38d003201a

Modified Files
--------------
doc/src/sgml/ref/create_language.sgml | 5 +--
src/backend/commands/define.c | 13 ------------
src/backend/commands/functioncmds.c | 22 ++++++--------------
src/backend/commands/proclang.c | 35 +++++++-------------------------
src/include/commands/defrem.h | 2 -
5 files changed, 17 insertions(+), 60 deletions(-)