x86_64: Call finite scalar versions in vectorized log, pow, exp (bz #20033).

Vector math functions require -ffast-math which sets -ffinite-math-only,
so it is needed to call finite scalar versions (which are called from
vector functions in some cases).

Since finite version of pow() returns qNaN instead of 1.0 for several
inputs, those inputs are excluded for tests of vector math functions.

    [BZ #20033]
    * sysdeps/x86_64/fpu/multiarch/svml_d_exp2_core_sse4.S: Call
    finite version.
    * sysdeps/x86_64/fpu/multiarch/svml_d_exp4_core_avx2.S: Likewise.
    * sysdeps/x86_64/fpu/multiarch/svml_d_exp8_core_avx512.S: Likewise.
    * sysdeps/x86_64/fpu/multiarch/svml_d_log2_core_sse4.S: Likewise.
    * sysdeps/x86_64/fpu/multiarch/svml_d_log4_core_avx2.S: Likewise.
    * sysdeps/x86_64/fpu/multiarch/svml_d_log8_core_avx512.S: Likewise.
    * sysdeps/x86_64/fpu/multiarch/svml_d_pow2_core_sse4.S: Likewise.
    * sysdeps/x86_64/fpu/multiarch/svml_d_pow4_core_avx2.S: Likewise.
    * sysdeps/x86_64/fpu/multiarch/svml_d_pow8_core_avx512.S: Likewise.
    * sysdeps/x86_64/fpu/multiarch/svml_s_expf16_core_avx512.S: Likewise.
    * sysdeps/x86_64/fpu/multiarch/svml_s_expf4_core_sse4.S: Likewise.
    * sysdeps/x86_64/fpu/multiarch/svml_s_expf8_core_avx2.S: Likewise.
    * sysdeps/x86_64/fpu/multiarch/svml_s_logf16_core_avx512.S: Likewise.
    * sysdeps/x86_64/fpu/multiarch/svml_s_logf4_core_sse4.S: Likewise.
    * sysdeps/x86_64/fpu/multiarch/svml_s_logf8_core_avx2.S: Likewise.
    * sysdeps/x86_64/fpu/multiarch/svml_s_powf16_core_avx512.S: Likewise.
    * sysdeps/x86_64/fpu/multiarch/svml_s_powf4_core_sse4.S: Likewise.
    * sysdeps/x86_64/fpu/multiarch/svml_s_powf8_core_avx2.S: Likewise.
    * sysdeps/x86_64/fpu/svml_d_exp2_core.S: Likewise.
    * sysdeps/x86_64/fpu/svml_d_log2_core.S: Likewise.
    * sysdeps/x86_64/fpu/svml_d_pow2_core.S: Likewise.
    * sysdeps/x86_64/fpu/svml_s_expf4_core.S: Likewise.
    * sysdeps/x86_64/fpu/svml_s_logf4_core.S: Likewise.
    * sysdeps/x86_64/fpu/svml_s_powf4_core.S: Likewise.
    * math/libm-test.inc (pow_test_data): Exclude tests for qNaN
    in power zero.