Suppress warnings generated by -Wwrite-strings

Here are suppressed warnings:

    src/fmt_fp.c: In function 'fmt_fp':
    src/fmt_fp.c:124:16: warning: initialization discards 'const' qualifier from pointer target type
         char *ss = (t&32)?"inf":"INF";
                    ^
    src/fmt_fp.c:125:17: warning: assignment discards 'const' qualifier from pointer target type
         if (y!=y) ss=(t&32)?"nan":"NAN";
                     ^
    mrbgems/mruby-string-ext/src/string.c: In function 'mrb_str_succ_bang':
    mrbgems/mruby-string-ext/src/string.c:302:27: warning: assignment discards 'const' qualifier from pointer target type
           if (e == b) prepend = "1";
                               ^
    mrbgems/mruby-string-ext/src/string.c:305:27: warning: assignment discards 'const' qualifier from pointer target type
           if (e == b) prepend = "a";
                               ^
    mrbgems/mruby-string-ext/src/string.c:308:27: warning: assignment discards 'const' qualifier from pointer target type
           if (e == b) prepend = "A";
                               ^
    mrbgems/mruby-bin-mruby/tools/mruby/mruby.c: In function 'main':
    mrbgems/mruby-bin-mruby/tools/mruby/mruby.c:213:13: warning: assignment discards 'const' qualifier from pointer target type
         cmdline = args.cmdline ? args.cmdline : "-";
                 ^
    mrbgems/mruby-bin-debugger/tools/mrdb/cmdbreak.c: In function 'print_breakpoint':
    mrbgems/mruby-bin-debugger/tools/mrdb/cmdbreak.c:159:3: warning: initialization discards 'const' qualifier from pointer target type
       char* enable_letter[] = {BREAK_INFO_MSG_DISABLE, BREAK_INFO_MSG_ENABLE};
       ^
    mrbgems/mruby-bin-debugger/tools/mrdb/cmdbreak.c:159:3: warning: initialization discards 'const' qualifier from pointer target type

1 files changed, 1 insertions, 1 deletions

diff --git a/src/fmt_fp.c b/src/fmt_fp.c
index a94503e63..9b29093a8 100644
--- a/src/fmt_fp.c
+++ b/src/fmt_fp.c
@@ -121,7 +121,7 @@ fmt_fp(struct fmt_args *f, long double y, int w, int p, int fl, int t)
   } else prefix++, pl=0;
 
   if (!isfinite(y)) {
-    char *ss = (t&32)?"inf":"INF";
+    const char *ss = (t&32)?"inf":"INF";
     if (y!=y) ss=(t&32)?"nan":"NAN";
     pad(f, ' ', w, 3+pl, fl&~ZERO_PAD);
     out(f, prefix, pl);