Add missing keywords

[TheWitheredStriker]

Fixes #137

Added the following (missing) keywords from Free Pascal:

• assembler
• cdecl
• cppdecl
• constref
• helper
• nostackframe
• oldfpccall
• pascal
• register
• stdcall

Reference: https://wiki.freepascal.org/Reserved_words

[TheWitheredStriker]

Added the following additional keywords:

Oxygene:

• add
• async
• autoreleasepool
• await
• block
• copy
• delegate
• deprecated
• each
• empty
• ensure
• enum
• event
• extension
• finalizer
• flags
• from (Also a LINQ keyword)
• future
• has
• implies
• inline
• invariants
• iterator
• lazy
• lifetimestrategy
• locked
• locking
• loop
• mapped
• matching
• method
• namespace
• nested
• new
• notify
• nullable
• old
• optional
• parallel
• params
• partial
• pinned
• queryable
• raises
• readonly
• remove
• require
• result
• sealed
• selector
• sequence
• soft
• static
• step
• strong
• tuple
• unconstrained
• unmanaged
• unretained
• using
• volatile
• weak
• where (Also a LINQ keyword)
• yield

LINQ (Oxygene):

• asc
• by
• concat
• desc
• distinct
• equals
• group
• into
• join
• order
• reverse
• select
• skip
• take

Other Delphi keywords:

• create
• platform
• reference
• safecall

Reference: https://docs.elementscompiler.com/Oxygene/Keywords/