Fix uninitialized cfg.colors[] element usage caught by Deuce (and Clang?)

Conditional jump or move depends on uninitialised value(s)
   at 0x4AE768D: sbbs_t::backfill(char const*, float, int, int) (con_out.cpp:1445)
   by 0x4AE7855: sbbs_t::progress(char const*, int, int, int) (con_out.cpp:1467)
   by 0x4AE91A9: ProgressLoadingMsgPtrs(void*, int, int) (data_ovl.cpp:27)
   by 0x4C7C577: getmsgptrs (userdat.c:3972)
   by 0x4AE9144: sbbs_t::getmsgptrs() (data_ovl.cpp:39)
   by 0x4BF9237: sbbs_t::logon() (logon.cpp:452)
   by 0x4AC1CE2: sbbs_t::answer() (answer.cpp:636)
   by 0x4C0FD37: node_thread(void*) (main.cpp:4277)

Introduced in commit 48e7520e (when colors was converted from a byte array
to a uint array), we weren't memsetting the right number of bytes.

Since color is not an array of ints (not bytes), memset (of non-zero values)
isn't really the right initialization approach anyway. Now using a for-loop.

src/sbbs3/load_cfg.c

@@ -413,6 +413,7 @@ bool read_attr_cfg(scfg_t* cfg, char* error, size_t maxerrlen)
     char    str[256];
 	long	offset=0;
     FILE    *instream;
+	int		i;
 
 	SAFEPRINTF(str,"%sattr.cfg",cfg->ctrl_dir);
 	if((instream=fnopen(NULL,str,O_RDONLY))==NULL) {
@@ -427,7 +428,8 @@ bool read_attr_cfg(scfg_t* cfg, char* error, size_t maxerrlen)
 		return(false);
 	}
 	/* Setup default colors here: */
-	memset(cfg->color,LIGHTGRAY|HIGH,MIN_COLORS);
+	for(i = 0; i < MIN_COLORS; ++i)
+		cfg->color[i] = LIGHTGRAY | HIGH;
 	cfg->color[clr_votes_full] = WHITE|BG_MAGENTA;
 	cfg->color[clr_progress_full] = CYAN|HIGH|BG_BLUE;
 	for(cfg->total_colors=0;!feof(instream) && !ferror(instream);cfg->total_colors++) {