Change the amount of HF exchange in functionals

Only for BLYP series:

$scf
RKS
DFT
# new functional with cX*HF+(1-cX)*B88
VBLYP 
hfexchange
0.0
charge
0
spin
1
THRESHCONV
1.d-12 1.d-10
OPTSCR
1
$end