Eliminate warning: unused parameter 'inst'

Add UNREFERENCED(_inst) to the instruction format E
decoder to prevent warning: unused parameter 'inst'
Eliminate warning: format expects argument of type unsigned int

pfpo.c: In function 'HFPlongGet':
pfpo.c:492:9: warning: format '%x' expects argument of type 'unsigned
int', but argument 3 has type 'U64' [-Wformat]
pfpo.c: In function 'HFPextGet':
pfpo.c:535:9: warning: format '%x' expects argument of type 'unsigned
int', but argument 3 has type 'U64' [-Wformat]
pfpo.c:541:9: warning: format '%x' expects argument of type 'unsigned
int', but argument 3 has type 'U64' [-Wformat]
Eliminate warning: function defined but not used

Bypass placeholder functions in pfpo.c pending completion
of corresponding PFPO functionality:

pfpo.c:56:13: warning: 'BFPshortGet' defined but not used
pfpo.c:140:13: warning: 'BFPlongGet' defined but not used
pfpo.c:224:13: warning: 'BFPextGet' defined but not used
pfpo.c:323:13: warning: 'DFPshortGet' defined but not used
pfpo.c:352:13: warning: 'DFPlongGet' defined but not used
pfpo.c:381:13: warning: 'DFPextGet' defined but not used
pfpo.c:419:13: warning: 'HFPshortGet' defined but not used
pfpo.c:460:13: warning: 'HFPlongGet' defined but not used
pfpo.c:501:13: warning: 'HFPextGet' defined but not used