Change pointers from char * to unsigned char *

Change pointers from char * to unsigned char *

GCC 4.2 complaints:

cc1: warnings being treated as errors
binutils/readelf.c:12057: warning: dereferencing type-punned pointer will break strict-aliasing rules

This patch silences this GCC warning.

	* readelf.c (dump_section_as_strings): Change pointers from
	char * to unsigned char *.