This patch implements PIC and non-PIC sibcall patterns for SH. I'm a bit unsure about whether it's more appropriate for `sibcalli' and `sibcalli_pcrel' and `sibcall_pcrel' to have type `jump_ind' or `call', but the way it is now (the latter is `call', the others are `jump_ind') appears to be working fine (i.e., no regressions in the testsuite). Ok to install?