Fix issue in hargreaves function

[lochbika]

This error only appears when using precipitation input and tsMatrix as input format.
The following code

# Load data for Tampa, lat=37.6475N, elevation=402.6 m. a.s.l.
# Data consists on monthly values since January 1980
data(wichita)
attach(wichita)
names(wichita)

# tsMatrix input (data from several stations)
# Replicating Wichita data twice to simulate data at two locations.
tmin <- cbind(TMIN, TMIN + 1.5)
tmax <- cbind(TMAX, TMAX + 1.5)
tmin <- ts(tmin, start=c(2000, 1), frequency = 12)
tmax <- ts(tmax, start=c(2000, 1), frequency = 12)
precip <- ts(matrix(runif(prod(dim(tmax)), min=0, max=23), ncol=2), start=c(2000, 1), frequency = 12)
lat <- c(37.6475, 35.000)
har <- hargreaves(tmin, tmax, lat = lat, Pre=precip, na.rm = TRUE)

give this error:

Error in `*.default`(0.0013 * 0.408 * Ra * (Tmean + 17), ab^0.76) :
non-conformable arrays

I fixed it by replacing Pre with Rs (see diff)
Rs is created inside the function with conformable array dimenstions

[sbegueria]

Have a look at this. This an option that hasn't been tested: matrix input, using pre option.