inlined from pexpr
* -an option that will write the secondpass nodes to the .s file, this
requires EXTDEBUG define to actually write the info
* fixed various internal errors and crashes due recent code changes
* register allocation is now handled by a class and is mostly processor
independent (+rgobj.pas and i386/rgcpu.pas)
* temp allocation is now handled by a class (+tgobj.pas, -i386\tgcpu.pas)
* some small improvements and fixes to the optimizer
* some register allocation fixes
* some fpuvaroffset fixes in the unary minus node
* push/popusedregisters is now called rg.save/restoreusedregisters and
(for i386) uses temps instead of push/pop's when using -Op3 (that code is
also better optimizable)
* fixed and optimized register saving/restoring for new/dispose nodes
* LOC_FPU locations now also require their "register" field to be set to
R_ST, not R_ST0 (the latter is used for LOC_CFPUREGISTER locations only)
- list field removed of the tnode class because it's not used currently
and can cause hard-to-find bugs
resulttype and first pass)
* made handling of read(ln)/write(ln) processor independent
* moved processor independent handling for str and reset/rewrite-typed
from firstpass to resulttype pass
* changed names of helpers in text.inc to be generic for use as
compilerprocs + added "iocheck" directive for most of them
* reading of ordinals is done by procedures instead of functions
because otherwise FPC_IOCHECK overwrote the result before it could
be stored elsewhere (range checking still works)
* compilerprocs can now be used in the system unit before they are
implemented
* added note to errore.msg that booleans can't be read using read/readln
