qemu: improve device flag parsing

qemu: improve device flag parsing

* src/qemu/qemu_capabilities.h (qemuCapsParseDeviceStr): New
prototype.
* src/qemu/qemu_capabilities.c (qemuCapsParsePCIDeviceStrs)
Rename and split...
(qemuCapsExtractDeviceStr, qemuCapsParseDeviceStr): ...to make it
easier to add and test device-specific checks.
(qemuCapsExtractVersionInfo): Update caller.
* tests/qemuhelptest.c (testHelpStrParsing): Also test parsing of
device-related flags.
(mymain): Update expected flags.
* tests/qemuhelpdata/qemu-0.12.1-device: New file.
* tests/qemuhelpdata/qemu-kvm-0.12.1.2-rhel60-device: New file.
* tests/qemuhelpdata/qemu-kvm-0.12.3-device: New file.
* tests/qemuhelpdata/qemu-kvm-0.13.0-device: New file.