Fixed github sdcc-gas issues #1, #2 and #4

Issue #1 was caused because code_name and data_name had been incorrectly
defined as const-qualified pointers, but this must be an exception for
the z80 backend, as stated by the comments.

Issue #2 has been solved by removing the --gas switch from SDCCmain.c,
renaming it to "--asm=" (as requested by PKK) and moved to STM8's main.c,
so the option is limited to those targets supporting it.

Issue #4 was because of SDCCglue.c, that generated local labels using
"!labeldef" instead of "!slabeldef", causing those __str_%d labels to be
printed as "__str_%d::" (the double colons stand for globa label according
to asxxx documentation) instead of "__str_%d":".

I ran the regression tests and most of them passed, but "wchar" returned another
"Multiple definition of..." error that I cannot explain so far. It is better than
nothing, though.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/port.h b/src/port.h
index 478fe3e..dbfd4c5 100644
--- a/src/port.h
+++ b/src/port.h
@@ -217,8 +217,8 @@ typedef struct
      * due to ugly implementation in gbz80 target;
      * this should be fixed in src/z80/main.c (borutr)
      */
-    const char *const code_name;
-    const char *const data_name;
+    const char *code_name;
+    const char *data_name;
     const char *const idata_name;
     const char *const pdata_name;
     const char *const xdata_name;