The QEMU 'sendkey' command expects keys to be encoded in the same
way as the RFB extended keycode set. Specifically it wants extended
keys to have the high bit of the first byte set, while the Linux
XT KBD driver codeset uses the low bit of the second byte. To deal
with this we introduce a new keymap 'RFB' and use that in the QEMU
driver

* include/libvirt/libvirt.h.in: Add VIR_KEYCODE_SET_RFB
* src/qemu/qemu_driver.c: Use RFB keycode set instead of XT KBD
* src/util/virkeycode-mapgen.py: Auto-generate the RFB keycode
  set from the XT KBD set
* src/util/virkeycode.c: Add RFB keycode entry to table. Add a
  verify check on cardinality of the codeOffset table

Also prepend $(AM_V_GEN) to the command line, mark virkeycode-mapgen.py
as executable and switch the shebang line from /bin/python to the
commonly use /usr/bin/python.

Add virtkey lib for usage-improvment and keycode translating.
Add 4 internal API for the aim

const char *virKeycodeSetTypeToString(int codeset);
int virKeycodeSetTypeFromString(const char *name);
int virKeycodeValueFromString(virKeycodeSet codeset, const char *keyname);
int virKeycodeValueTranslate(virKeycodeSet from_codeset,
                             virKeycodeSet to_offset,
                             int key_value);

* include/libvirt/libvirt.h.in: extend virKeycodeSet enum
* src/Makefile.am: add new virtkeycode module and rule to generate
  virkeymaps.h
* src/util/virkeycode.c src/util/virkeycode.h: new module
* src/util/virkeycode-mapgen.py: python generator for virkeymaps.h
  out of keymaps.csv
* src/libvirt_private.syms: extend private symbols for new module
* .gitignore: add generated virkeymaps.h