The qemu_conf.c code is doing three jobs, driver config file
loading, QEMU capabilities management and QEMU command line
management. Move the capabilities code into its own file
* src/qemu/qemu_capabilities.c, src/qemu/qemu_capabilities.h: New
capabilities management code
* src/qemu/qemu_conf.c, src/qemu/qemu_conf.h: Delete capabilities
code
* src/qemu/qemu_conf.h: Adapt for API renames
* src/Makefile.am: add src/qemu/qemu_capabilities.c