Update p_conv.c
Update p_conv.c

Inserted the function for calculating convolution; considers the first nh-th items in *x as padding
olajep/pal,mateunho/pal,Adamszk/pal3,parallella/pal,twocs/pal,Adamszk/pal3,8l/pal,aolofsson/pal,mateunho/pal,eliteraspberries/pal,parallella/pal,debug-de-su-ka/pal,8l/pal,8l/pal,Adamszk/pal3,aolofsson/pal,eliteraspberries/pal,RafaelRMA/pal,debug-de-su-ka/pal,aolofsson/pal,parallella/pal,debug-de-su-ka/pal,eliteraspberries/pal,olajep/pal,twocs/pal,parallella/pal,mateunho/pal,twocs/pal,eliteraspberries/pal,mateunho/pal,8l/pal,parallella/pal,olajep/pal,RafaelRMA/pal,twocs/pal,debug-de-su-ka/pal,aolofsson/pal,eliteraspberries/pal,mateunho/pal,RafaelRMA/pal,debug-de-su-ka/pal,RafaelRMA/pal,Adamszk/pal3,olajep/pal