parse constants from lea instruction as both number and offset features

we often see the lea instruction used for arithmetic e.g.

lea eax, [eax+61C88647h]

where in the above example 0x61C88647 is a magic value used in the tiny encryption algorithm (TEA).

Currently we parse 0x61C88647 as an offset feature but ideally we would also parse the value as a number feature to allow more concise rule writing. Parsing as both offset and number features would only apply to lea instructions.

Pros:

• more concise rules for situations where lea is used for arithmetic

Cons:

• we potentially generate many additional number features

[mr-tz]

dup of #320 😄

[williballenthin]

e.g.