gdb.base/find.exp C++ify

gdb.base/find.exp C++ify

This makes the testcase work when compiled with C++ compiler.

We need #include <string.h> for memset.

gdb/testsuite/ChangeLog:

	* gdb.base/find.c: Include <string.h>.
	(init_bufs): Add cast.
	* gdb.base/find.exp: Issue "set print asm-demangle on".