fexc: Warn when decompiling a malformed section entry (key string)

script_bin.c decompiles section entries even if they have invalid
indentifiers. Thus malformed .bin files were observed to result in
a .fex that couldn't be processed successfully with the sunxi-fexc
compiler.

This patch makes bin2fex now issue a warning for this kind of keys,
so that they're easier to notice and correct.
Signed-off-by: Bernhard Nortmann <bernhard.nortmann@web.de>

script_bin.c

@@ -17,6 +17,7 @@
 
 #include "common.h"
 
+#include <ctype.h>
 #include <errno.h>
 #include <stdlib.h>
 #include <stdint.h>
@@ -240,6 +241,13 @@ static int decompile_section(void *bin, size_t bin_size,
 		type	= (entry->pattern >> 16) & 0xffff;
 		words	= (entry->pattern >>  0) & 0xffff;
 
+		for (char *p = entry->name; *p; p++)
+			if (!(isalnum(*p) || *p == '_')) {
+				pr_info("Warning: Malformed entry key \"%s\"\n",
+					entry->name);
+				break;
+			}
+
 		switch(type) {
 		case SCRIPT_VALUE_TYPE_SINGLE_WORD: {
 			uint32_t *v = data;