Function: bitneg
Section: conversions
C-Name: gbitneg
Prototype: GD-1,L,
Help: bitneg(x,{n=-1}): bitwise negation of an integers x truncated to n
 bits. n=-1 means represent infinite sequences of bit 1 as negative numbers.
 Negative numbers behave as if modulo big power of 2.
Doc:
 \idx{bitwise negation} of an integer $x$,
 truncated to $n$ bits, $n\geq 0$, that is the integer
 $$\sum_{i=0}^{n-1} \kbd{not}(x_i) 2^i.$$
 The special case $n=-1$ means no truncation: an infinite sequence of
 leading $1$ is then represented as a negative number.

 See \secref{se:bitand} for the behavior for negative arguments.
