log10 generate wrong odd result when input is a float type number equal to pow(1.0, a negative even number)

[a5632645]

When input is 1.0 to a negative even float type number, gcem::log10 return a wrong negative odd number.

Eg: gcem::log10(0.01) = -1.0f, should be -2.0f

Tested with 1e-2f to 1e-26f, only the 1e-22f is right.
In double and long double type, this also happens to 1e-12 and 1e-14.

Envrioment: MSVC 14.41.33901, C++20 std
GCE-Math version 1.18.0

[MitchellThompkins]

I think this is the same bug that I identified in #59 and have a proposed fix for in #60. On 012ae73 I get this behavior:

printf("std::log10(0.01L) = %.25LE\n", std::log10(0.01L));
printf("gcem::log10(0.01L) = %.25LE\n", gcem::log10(0.01L));

std::log10(0.01L) = -2.0000000000000000000000000E+00
gcem::log10(0.01L) = -1.0000000000000000001084202E+00

with my proposed fixes I get:

std::log10(0.01L) = -2.0000000000000000000000000E+00
gcem::log10(0.01L) = -2.0000000000000000000000000E+00

All variants of gcem::log call gcem::find_exponent which suffers from a boundary exclusion bug when calculating the exponent.