incorrect handling of multiline fribidi transformations

[tbonfort]

When the input text in a right-to-left language contains a newline caracter, the fribidi transformed text will be rendered from bottom-to-top which is not usually wanted

here's an example in latin characters for readability:

input text:

Casa
Blanca

fribidi transformed text:

acnalB
asaC

When a native speaker reads that text, it end up being:

Blanca
Casa

which is incorrect.

In the case where we do not have a bottom-to-top language, the fribidi calls should be done line by line, after having split the input string on carriage returns.