math: add an expm1l special case

[libc-test] / src / math / sanity / scalbnf.h

T(RN,   -0x1.0223ap+3,          -2,   -0x1.0223ap+1,          0x0p+0, 0)
T(RN,   0x1.161868p+2,          -1,   0x1.161868p+1,          0x0p+0, 0)
T(RN,  -0x1.0c34b4p+3,           0,  -0x1.0c34b4p+3,          0x0p+0, 0)
T(RN,   -0x1.a206fp+2,           1,   -0x1.a206fp+3,          0x0p+0, 0)
T(RN,   0x1.288bbcp+3,           2,   0x1.288bbcp+5,          0x0p+0, 0)
T(RN,    0x1.52efdp-1,           3,    0x1.52efdp+2,          0x0p+0, 0)
T(RN,  -0x1.a05cc8p-2,           4,  -0x1.a05cc8p+2,          0x0p+0, 0)
T(RN,   0x1.1f9efap-1,           5,   0x1.1f9efap+4,          0x0p+0, 0)
T(RN,    0x1.8c5dbp-1,           6,    0x1.8c5dbp+5,          0x0p+0, 0)
T(RN,  -0x1.5b86eap-1,           7,  -0x1.5b86eap+6,          0x0p+0, 0)