Support multiline error/warning reports
Currently reports have no proper output if they have source-references spanning multiple lines.
Maybe even some improvements to the current single line reports could be done.
void main () {
try {
} catch (Error e) {
}
}
$ valac -C test.vala
test.vala:3.10-4.2: warning: unreachable catch clause detected
Compilation succeeded - 1 warning(s)