Fix demangler testsuite crashes with CP_DEMANGLE_DEBUG defined

Fix demangler testsuite crashes with CP_DEMANGLE_DEBUG defined

Running the demangler's testsuite with CP_DEMANGLE_DEBUG defined
crashes, with:

 Program received signal SIGSEGV, Segmentation fault.
 0x000000000040a8c3 in d_dump (dc=0x1, indent=12) at ../../src/libiberty/cp-demangle.c:567
 567       switch (dc->type)

 (gdb) bt 3
 #0  0x000000000040a8c3 in d_dump (dc=0x1, indent=12) at ../../src/libiberty/cp-demangle.c:567
 #1  0x000000000040ae47 in d_dump (dc=0x7fffffffd098, indent=10) at ../../src/libiberty/cp-demangle.c:787
 #2  0x000000000040ae47 in d_dump (dc=0x7fffffffd0c8, indent=8) at ../../src/libiberty/cp-demangle.c:787

Note dc=0x1, which is obviously a bogus pointer.  This is the end of
d_dump recursing for a component type that that doesn't actually have
subtrees:

 787       d_dump (d_left (dc), indent + 2);
 788       d_dump (d_right (dc), indent + 2);

This fixes the two cases the testsuite currently trips on.

libiberty/
2014-05-28  Pedro Alves  <palves@redhat.com>

	* cp-demangle.c (d_dump): Handle DEMANGLE_COMPONENT_FUNCTION_PARAM
	and DEMANGLE_COMPONENT_NUMBER.