rpeep(): silence compiler warning

rpeep(): silence  compiler warning

op.c: In function ‘Perl_rpeep’:
op.c:13666:35: warning: comparison is always false due to limited range of data
type [-Wtype-limits]

This condition is always false if for example base is 32 bit and UVs are 64
bit:

    base >  (UV_MAX >> (OPpPADRANGE_COUNTSHIFT+SAVE_TIGHT_SHIFT)

silence the warning by replacing base with a constant-folded conditional

    (cond ? base : 0) > ....

where cond is false if sizeof(base) is small.