libril: allow board to provide libril

Change-Id: If0033865ab179854c27c56eaaf078fcc30ea102a
Don't use the clientId argument with non-qcom hardware

Other modems' implementations won't know how to deal with it, and
some are confirmed to simply reject the RIL_Init call.

If the hardware isn't qualcomm, just skip the whole multi-ril stuff
entirely

Change-Id: I132a4d7fc3d4532b2015f7e95863fac78889f833

rild: Weaken the RIL_setRilSocketName symbol

custom libril implementations won't have it, but its lack isn't
fatal outside of multi-SIM

Change-Id: If8312078921bb4ed756dcd86e17e85847638c155

rild: Unbreak multi-SIM socket name

Change-Id: Icae742c42c45726105d1a9e07a26bc4d10cc82bf

Weaken external rild symbol.

Not all libril will have this

Change-Id: I3da165f5cf779a02c7eb168d6e3c9b398d284835

Change-Id: If8312078921bb4ed756dcd86e17e85847638c155