* Fixes
CC backend: goto (needs test), 
sort with non-default comparison. 
last for non-loop blocks (needs simplier test, test 29).
improve XSUB handling (both static and dynamic, needs tests)
sv_magic can do SvREFCNT_inc(obj) which messes up precalculated refcounts
allocation of XPV[INAHC]V structures needs fixing: Perl tries to free
  them, whereas the compiler expects them to be linked to a xpv[inahc]v_root
list the same as X[IPR]V structures.
ref counts
perl_parse replacement
compile-time initialisation of AvARRAYs
signed/unsigned problems with NV (and IV?) initialisation and elsewhere?
CvOUTSIDE for ordinary subs
DATA filehandle for C-compiled program (hard)
* Features
type checking: Devel::TypeCheck
compile time v. runtime initialisation
save PMOPs in compiled form
selection of what to dump
options for cutting out line info (COP elimination) etc.
comment output
shared constants
check module dependencies, vs. link libs static, not via DynaLoader
new Asm, JIT or PIR backend, PLJC ByteLoader magic
check Bytecode op coverage in the tests, should cover all ops 0-142
ByteLoader compatibility: version, platform. eventually Bytecode version 
  portability (test with 5.6 on cygwin, partially done)
* Optimisations
collect static strings beforehand, such as GvNAMEs, COP FILENAME (for pre 5.10)
  and GV method names package::name. (partially done)
proper static init of PMOP SV's (only works dynamic >= 5.10)
proper static init of PVBM/FBM
collapse LISTOPs to UNOPs or BASEOPs
compile-time qw(), constant subs
global analysis of variables, type hints etc.
  Devel::TypeCheck instead of magic variable _ir, ... suffices
  e.g. mark IVonly SV's and magic/flags change functions and 
  optimize all op subtrees for the compiled backends to use direct ints
demand-loaded bytecode (leader of each basic block replaced by an op
  which loads in bytecode for its block)
fast sub calls for CC backend