Add functions for bitwise operations

[haozhun]

Considerations:

• future support of DECIMAL types
• same result regardless of type
• not commit to stores numbers as two's complement internally

Functions that are insensitive to width of numbers:

BITWISE_NOT(1) = -2 -- document as bitwise NOT in two's complement arithmetic
BITWISE_AND(91, 15) = 11
BITWISE_OR(32, 3) = 35
BITWISE_XOR(17, 5) = 20
BITWISE_ARSH(-8, 2) = -2

Function that has tricky overflow issue:

BITWISE_LSH(7, 2, 4) = 12 -- treat 7 as a 4-bit signed number and left shift by 2,
                          -- truncate overflow

Function that are inherently sensitive to width of numbers:

BITWISE_LRSH(-8, 2, 5) = 6 -- treat -8 as a 5-bit signed number and lsh by 2
BITCOUNT(-8, 6) = 3 -- treat -8 as a 6-bit signed number and count 1s
                    -- alias POPCOUNT

Placeholder functions:

BITWISE_RSH: tell user to choose one of BITWISE_ARSH and BITWISE_LRSH
BITWISE_LRSH: tell user to provide 3rd parameter
BITCOUNT: tell user to provide 2nd parameter
BITWISE_LSH: tell user to provide 3rd parameter

[haozhun]

@martint Please take a look.

[haozhun]

@martint Does the proposed function signatures look right to you?

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[tdcmeehan]

Reopening since bitshift functions are still outstanding

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