Rule 20.5 : Deprecated use of errno

These are typically seen when the C std requires setting errno.

./src/alloc.c
./src/file_pos.c
./src/math_longdouble.c
./src/mbstring.c
./src/sc/asin_StarCore.c
./src/sc/atan2_StarCore.c
./src/sc/exp_StarCore.c
./src/sc/file_io_StarCore.c
./src/sc/math_StarCore.c
./src/sc/signal_StarCore.c
./src/sc/sqrt_StarCore.c
./src/sc/time_StarCore.c
./src/signal.c
./src/strtold.c
./src/strtoul.c
./src/sun_math/Double_precision/e_acos.c
./src/sun_math/Double_precision/e_asin.c
./src/sun_math/Double_precision/e_atanh.c
./src/sun_math/Double_precision/e_log.c
./src/sun_math/Double_precision/e_log10.c
./src/sun_math/Double_precision/e_pow.c
./src/sun_math/Double_precision/e_sqrt.c
./src/sun_math/Double_precision/k_standard.c
./src/sun_math/math_sun.c
./src/wcstold.c
./src/wcstoul.c