symfile, vdso: remove target sections

Target sections added by the add-symbol-file-from-memory command are not
removed when the process exits.  In fact, they are not removed, at all.

This causes GDB to crash in gdb.base/break-interp.exp.

Change the owner of those target sections to the object file generated in
symbol_file_add_from_memory and generalize the free_objfile observer in
symfile.c to remove target sections of any freed object file.
Skip hbreak-unmapped.exp if memory at address 0 is readable

hbreak-unmapped.exp assumes that memory at address 0 is unmapped or
unreadable, but on bare metal or uclinux targets, memory at address
0 is readable.  For example, on arm-none-eabi, the vector table base
address is 0x0.

hbreak *0^M
Hardware assisted breakpoint 3 at 0x0: file
/scratch/yqi/arm-none-eabi-lite/obj/cs3-2014.11-999999-arm-none-eabi-i686-pc-linux-gnu/generated/arm-vector.S,
line 25.^M
(gdb) FAIL: gdb.base/hbreak-unmapped.exp: hbreak *0
info break^M
Num     Type           Disp Enb Address    What^M
3       hw breakpoint  keep y   0x00000000
/scratch/yqi/arm-none-eabi-lite/obj/cs3-2014.11-999999-arm-none-eabi-i686-pc-linux-gnu/generated/arm-vector.S:25^M
(gdb) FAIL: gdb.base/hbreak-unmapped.exp: info break shows hw breakpoint
delete $bpnum

This patch is to check whether address 0 is readable via command 'x 0'.
If it is, skip the test.

gdb/testsuite:

2014-06-06  Yao Qi  <yao@codesourcery.com>

	* gdb.base/hbreak-unmapped.exp: Read memory at address 0.  If
	readable, skip the test.
add -q in help info and doc
Remove preprocessor conditionals for ANSI-standard signals

The six signals SIGINT, SIGILL, SIGABRT, SIGFPE, SIGSEGV and SIGTERM
are ANSI-standard and thus guaranteed to be available.  This patch
removes all preprocessor conditionals relating to these symbols.

gdb/
2014-06-06  Gary Benson  <gbenson@redhat.com>

	* common/signals.c: Remove preprocessor conditionals for
	always-defined signals SIGINT, SIGILL, SIGABRT, SIGFPE,
	SIGSEGV and SIGTERM.
	* proc-events.c: Likewise.

gdb/testsuite/
2014-06-06  Gary Benson  <gbenson@redhat.com>

	* gdb.base/call-signals.c: Remove preprocessor conditionals
	for always-defined signals SIGINT, SIGILL, SIGABRT, SIGFPE,
	SIGSEGV and SIGTERM.
	* gdb.base/sigall.c: Likewise.
	* gdb.base/unwindonsignal.c: Likewise.
	* gdb.reverse/sigall-reverse.c: Likewise.
update ChangeLog