Add support of coprocessor cp15, cp14 registers exposion in the embedded gdb server

[Anton Kochkov]

Please add support of exposion of ARM coprocesor registers/logic at the embedded gdb server,
 for example of cp15, cp14, etc registers.

Related project http://jtagarmgdbsrvr.sourceforge.net/index.html

Also filled bug in the GDB http://sourceware.org/bugzilla/show_bug.cgi?id=12602

[Peter Maydell (pmaydell)]

Since QEMU 3.0 the QEMU gdb stub supports read-only access to most cp14/cp15 registers. The gdb 'info all-registers' command will print all the registers (integer, fp and system registers), or individual registers can be read with commands like "print /x $SCTLR".

Write access isn't supported (that is a lot trickier to do in a reliable way since QEMU's internals make assumptions that system registers can only be changed in the ways that the guest validly can, and there's no easy API to connect to the debug stub that would allow the user to change system registers in only safe ways).