op.h: Use PERL_UNIQUE_NAME to make code more readable

This allows a variable name in a macro to be used that doesn't have much
extra verbiage that otherwise would be required to make it distinct from
other variables.

Author: khwilliamson

op.h

@@ -318,10 +318,11 @@ struct pmop {
    more complex, and we'd have an AV with (SV*)NULL in it, which feels bad */
 /* BEWARE - something that calls this macro passes (r) which has a side
    effect.  */
+#define r1_  PERL_UNIQUE_NAME(r)
 #define PM_SETRE(o,r)	STMT_START {					\
-                            REGEXP *const pm_setre_ = (r);		\
-                            assert(pm_setre_);				\
-                            PM_SETRE_raw(o, pm_setre_);                 \
+                            REGEXP *const r1_ = (r);		        \
+                            assert(r1_);				\
+                            PM_SETRE_raw(o, r1_);                       \
                         } STMT_END
 #else
 #define PM_GETRE_raw(o) ((o)->op_pmregexp)