Fix for bnc 976627.  Under high reg pressure constants need to be reloaded
from the TOC, and when it was floating point constants that reload
from the TOC wasn't accepted.

--- gcc/config/rs6000/rs6000.c.mm	2016-04-25 20:51:23.033619239 +0200
+++ gcc/config/rs6000/rs6000.c	2016-04-25 20:51:47.413926002 +0200
@@ -17094,6 +17094,7 @@ rs6000_secondary_reload_inner (rtx reg,
     case FLOAT_REGS:
       if (legitimate_indirect_address_p (addr, false)	/* reg */
 	  || legitimate_indexed_address_p (addr, false)	/* reg+reg */
+	  || legitimate_constant_pool_address_p (addr, mode, false)
 	  || ((GET_MODE_SIZE (mode) == 4 || GET_MODE_SIZE (mode) == 8)
 	      && and_op2 == NULL_RTX
 	      && scratch_or_premodify == scratch