tccpp: cleanup target-os defines

moved target_machine defines to the <target>-gen.c files.

Also:
- c2str.c moved into conftest.c
- tccdefs.h ; defined(__TINYC__) && !defined(_LOCORE) removed
  (in tinycc __TINYC__ is always defined and _LO... is never.)
- stddef.h : too many #ifdefs, removed
- tccgen.c:stabs: support win32 long doubles aka doubles.
- win32: math.h/tcc_libm.h: fix pointer mismatch in modfl
- tccpp.c: increment include_stack_ptr after the file was
  actually found otherwise it would print
  "in file included from <itself>: file not found..."

c67-gen.c

@@ -114,8 +114,12 @@ enum {
 #define USING_GLOBALS
 #include "tcc.h"
 
+ST_DATA const char *target_machine_defs =
+    "__C67__\0"
+    ;
+
 ST_DATA const int reg_classes[NB_REGS] = {
-    /* eax */ RC_INT | RC_FLOAT | RC_EAX, 
+    /* eax */ RC_INT | RC_FLOAT | RC_EAX,
     // only allow even regs for floats (allow for doubles)
     /* ecx */ RC_INT | RC_ECX,
     /* edx */ RC_INT | RC_INT_BSIDE | RC_FLOAT | RC_EDX,