Commit 0a459cec9 left this for later, but since time's running out, I went ahead and took care of it. There are more data types that somebody might someday want RANGE support for, but this is enough to satisfy all expectations of the SQL standard, which just says that "numeric, datetime, and interval" types should have RANGE support.
8b29e88cdc Add window RANGE support for float4, float8, numeric.
src/backend/utils/adt/float.c | 87 ++++++++++++++++
src/backend/utils/adt/numeric.c | 75 ++++++++++++++
src/include/catalog/catversion.h | 2 +-
src/include/catalog/pg_amproc.h | 3 +
src/include/catalog/pg_proc.h | 6 ++
src/test/regress/expected/window.out | 185 +++++++++++++++++++++++++++++++++++
src/test/regress/sql/window.sql | 72 ++++++++++++++
7 files changed, 429 insertions(+), 1 deletion(-)