remove a branch in SvIV_please_nomg

On VC 2003 and GCC 4.6.3, this patch decreases from 3 branches to
2 branches that machine code that makes up SvIV_please_nomg. Functionality
should be identical as before. This is intended to make math functions like
pp_add faster. Due to complexity/my time, SvIV_please wasn't optimized.
"(SvNOK(sv) || SvPOK(sv)" was optimized to
"(SvFLAGS(sv) & (SVf_NOK|SVf_POK))" on GCC and VC 2003 before this patch,
so that change reenforces what the optimizer already did before.

.text section of miniperl.exe size in bytes
gcc 32b 4.6.3 -O2 before 0x10d154
gcc 32b 4.6.3 -O2 after  0x10d064
vc2003            before 0xa4odf
vc2003            after  0xa406f