cleanup: unused ifdef'd code in IPPL

The following macros are never set or used:

• IPPL_COMM_ALARMS see #412 (closed)
• IPPL_GDL see #413 (closed)
• IPPL_DIRECTIO see #414 (closed)
• IPPL_IOFLAG_BUG see #415 (closed)
• IPPL_MPIXX see #416 (closed)
• IPPL_NETCDF see #417 (closed)
• IPPL_PM se #421 (closed)
• IPPL_PRINTDEBUG see #422 (closed)
• IPPL_PURIFY see #424 (closed)
• IPPL_RUNTIME_ERRCHECK see #419 (closed)
• IPPL_SGI_PRAGMAS see #427 (closed)
• IPPL_SHMEMPI see #421 (closed)
• IPPL_TFLOP see #428 (closed)
• IPPL_USE_PARTIAL_SPECIALIZATION (if not defined) see #430 (closed)
• IPPL_USE_FUNKY_VEC_COPIES see #431 (closed)
• IPPL_USE_MEMBER_TEMPLATES see #443 (closed)
• IPPL_USE_STANDARD_HEADERS see #440 (closed)
• IPPL_USE_RAND_RNG see #441 (closed)
• IPPL_USE_SIMPLE_RNG see #441 (closed)
• IPPL_USE_XCI_RNG see #441 (closed)
• IPPL_USE_SINGLE_PRECISION see #437 (closed)
• IPPL_XT3 see #436 (closed)
• OLD_IPPL_PGI see #434 (closed)
• SGI_TIMERS see #428 (closed)
• TULIP_TIMERS see #428 (closed)
• __MWERKS__ see #429 (closed)
• HAVE_EXPDE (and subsequently ParticleLayoutFromGrid.h) see #444 (closed)
• IPPL_DKS_MIC see #445 (closed)
• OLD_SWAP_PARTICLES see #446 (closed)
• UNDEFINED see #448 (closed)

What can be removed? @snuverink_j @frey_m @kraus @adelmann : please check what can be removed!

All ticked will be removed!