qemu/x86_64: update to use kernel 3.6.6

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

board/qemu/x86_64/readme.txt

@@ -4,4 +4,4 @@ Run the emulation with:
 
 The login prompt will appear in the graphical window.
 
-Tested with QEMU 1.1.1
+Tested with QEMU 1.2.0

configs/qemu_x86_64_defconfig

@@ -9,12 +9,12 @@ BR2_TARGET_GENERIC_GETTY_PORT="tty1"
 BR2_TARGET_ROOTFS_EXT2=y
 # BR2_TARGET_ROOTFS_TAR is not set
 
-# Lock to 3.5 headers to avoid breaking with newer kernels
-BR2_KERNEL_HEADERS_3_5=y
+# Lock to 3.6 headers to avoid breaking with newer kernels
+BR2_KERNEL_HEADERS_3_6=y
 
 # Kernel
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION=y
-BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="3.5.4"
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="3.6.6"
 BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG=y
-BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE="board/qemu/x86_64/linux-3.5.config"
+BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE="board/qemu/x86_64/linux-3.6.config"