Add general support in the function parser for "integer functions"
(actually implemented as special unary operators, then wrapped in
macros) and implement a family of integer logarithms. The only
difference is the behavior on a non-power-of-two argument:
ilog2[e] -- throw an error
ilog2w -- throw a warning
ilog2f -- round down to power of 2
ilog2c -- round up to power of 2
This is useful for back-converting from masks to bit values.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
