bugfix: lib/runscripts/table.run: map_table(): moved $map_table to global var so it can be used by other functions

bugfix: lib/runscripts/table.run: postprocess(): don't propagate $remake to remake_VegBIEN_mappings(), since this will cause map.csv to be remade, which is not related to the postprocessing.

lib/runscripts/table.run: map_table(): util.set_col_names_with_metadata(): removed unnecessary cast to regclass, which is performed implicitly. this used to be needed when the polymorphic util.rename_cols() was used instead.

schemas/util.sql: added trim(), which trims a table to include only original columns, as defined by a map table

schemas/util.sql: added derived_cols(), which gets table_'s derived columns (all the columns not in the names table)

schemas/util.sql: added eval2set()

schemas/util.sql: added drop_column()

inputs/REMIB/Specimen/postprocess.sql: map_nulls__*(): turned off STRICT to allow dynamic inlining, which speeds up the mk_derived_col() statements by 5x (342799.823 ms -> 71533.252 ms (6 min -> 1 min) for latitude_sec)

inputs/REMIB/Specimen/postprocess.sql: runtimes: updated for vegbiendev, before dynamic inlining. the times are about twice as fast as on starscream, so vegbiendev is faster at whatever is the limiting speed factor (probably not CPU, based on other benchmarks).

schemas/util.sql: map_nulls(): documented that due to dynamic inlining, this is just as fast as util._map() which it wraps. dynamic inlining now brings altogether a 40x speed improvement to map_nulls() (4000 ms -> 100 ms), and would likely bring a comparable improvement for other functions that are run repeatedly and call other user-defined functions.