Enable OpenMP backends for more Visual Studio builds
Enable OpenMP backends for more Visual Studio builds

`ALPAKA_ACC_CPU_B_SEQ_T_OMP2_ENABLE` backend historically had been disabled
due to the compilation times but without travis ther is no hard boundary
anymore that we could reach.

This also fixes the mention of `ALPAKA_ACC_CPU_BT_OMP4_ENABLE` by replacing
it with `ALPAKA_ACC_ANY_BT_OMP5_ENABLE`

BenjaminW3/alpaka,BenjaminW3/alpaka