add sys.sizeof_byte, _word, _float constants

because Antlr doesn't allow the grammar to contain a sizeof(typename) rule to override the sizeof(identifier) rule

compiler/res/prog8lib/atari/syslib.p8

@@ -23,6 +23,10 @@ sys {
 
     const ubyte target = 8         ;  compilation target specifier.  64 = C64, 128 = C128,  16 = CommanderX16, 8 = atari800XL
 
+    const ubyte sizeof_byte = 1
+    const ubyte sizeof_word = 2
+    const ubyte sizeof_float = 0    ; undefined, no float support
+
     asmsub  init_system()  {
         ; Initializes the machine to a sane starting state.
         ; Called automatically by the loader program logic.

compiler/res/prog8lib/c128/syslib.p8

@@ -351,6 +351,11 @@ sys {
 
     const ubyte target = 128         ;  compilation target specifier.  64 = C64, 128 = C128,  16 = CommanderX16.
 
+    const ubyte sizeof_byte = 1
+    const ubyte sizeof_word = 2
+    const ubyte sizeof_float = 5
+
+
 asmsub  init_system()  {
     ; Initializes the machine to a sane starting state.
     ; Called automatically by the loader program logic.

compiler/res/prog8lib/c64/syslib.p8

@@ -347,6 +347,10 @@ sys {
 
     const ubyte target = 64         ;  compilation target specifier.  64 = C64, 128 = C128, 16 = CommanderX16.
 
+    const ubyte sizeof_byte = 1
+    const ubyte sizeof_word = 2
+    const ubyte sizeof_float = 5    ; undefined, no float support
+
 
 asmsub  init_system()  {
     ; Initializes the machine to a sane starting state.

compiler/res/prog8lib/cx16/syslib.p8

@@ -1360,6 +1360,10 @@ sys {
 
     const ubyte target = 16         ;  compilation target specifier.  64 = C64,  128 = C128,  16 = CommanderX16.
 
+    const ubyte sizeof_byte = 1
+    const ubyte sizeof_word = 2
+    const ubyte sizeof_float = 5
+
 asmsub  init_system()  {
     ; Initializes the machine to a sane starting state.
     ; Called automatically by the loader program logic.

compiler/res/prog8lib/pet32/syslib.p8

@@ -98,6 +98,11 @@ sys {
 
     const ubyte target = 32         ;  compilation target specifier.  64 = C64, 128 = C128,  16 = CommanderX16, 32=PET
 
+    const ubyte sizeof_byte = 1
+    const ubyte sizeof_word = 2
+    const ubyte sizeof_float = 0    ; undefined, no floats supported
+
+
 asmsub  init_system()  {
     ; Initializes the machine to a sane starting state.
     ; Called automatically by the loader program logic.

compiler/res/prog8lib/virtual/syslib.p8

@@ -7,6 +7,11 @@ sys {
 
     const ubyte target = 255         ;  compilation target specifier.  64 = C64, 128 = C128,  16 = CommanderX16, 8 = atari800XL, 255 = virtual
 
+    const ubyte sizeof_byte = 1
+    const ubyte sizeof_word = 2
+    const ubyte sizeof_float = 8
+
+
     sub  reset_system()  {
         ; Soft-reset the system back to initial power-on Basic prompt.
         %ir {{

docs/source/todo.rst

@@ -1,6 +1,8 @@
 TODO
 ====
 
+see github for issues
+
 Regenerate skeleton doc files.
 
 Improve register load order in subroutine call args assignments:

examples/test.p8

@@ -1,18 +1,13 @@
-; EXAMPLE external command source code
-
-%launcher none
-%option no_sysinit
-%zeropage basicsafe
-%encoding iso
 %import textio
-%address $4000
+%zeropage basicsafe
 
-
-main $4030 {
-    %option force_output
-
-    sub start()  {
-        txt.print("external command\n")
-        sys.exit(0)
+main {
+    sub start() {
+        txt.print_ub(sys.sizeof_byte)
+        txt.spc()
+        txt.print_ub(sys.sizeof_word)
+        txt.spc()
+        txt.print_ub(sys.sizeof_float)
+        txt.nl()
     }
 }