Make the linker return an error status if it fails to merge ARM binaries with

different architecture tags.  Add a test case to make sure that this works,
and update readelf so that it will not seg-fault when trying to display the
attributes of binaries with invalid architecture tags.

	* elf32-arm.c (elf32_arm_merge_eabi_attributes): Return false if
	failed to merge.

	* ld-arm/attr-merge-arch-2.d: New test case.
	* ld-arm/attr-merge-arch-2a.s: New test case source file.
	* ld-arm/attr-merge-arch-2b.s: Likewise.
	* ld-arm/arm-elf.exp: Run new test case.

	* readelf.c (display_arm_attribute): Use unsigned int type for
	tag, val and type variables.

binutils/readelf.c

@@ -11548,10 +11548,10 @@ display_tag_value (int tag,
 /* ARM EABI attributes section.  */
 typedef struct
 {
-  int tag;
+  unsigned int tag;
   const char * name;
   /* 0 = special, 1 = string, 2 = uleb123, > 0x80 == table lookup.  */
-  int type;
+  unsigned int type;
   const char ** table;
 } arm_attr_public_tag;
 
@@ -11669,12 +11669,12 @@ static unsigned char *
 display_arm_attribute (unsigned char * p,
 		       const unsigned char * const end)
 {
-  int tag;
+  unsigned int tag;
   unsigned int len;
-  int val;
+  unsigned int val;
   arm_attr_public_tag * attr;
   unsigned i;
-  int type;
+  unsigned int type;
 
   tag = read_uleb128 (p, &len, end);
   p += len;