Allow named configurations to be specified via the CONFIG=... build
parameter.  For headers in config/*.h which support named
configurations, the following files will be included when building
with CONFIG=<name>:

  - config/defaults/<platform>.h (e.g. config/defaults/pcbios.h)

  - config/<header>.h

  - config/<name>/<header>.h (only if the directory config/<name> exists)

  - config/local/<header>.h (autocreated if necessary)

  - config/local/<name>/<header>.h (autocreated if necessary)

This mechanism allows for predefined named configurations to be
checked in to the source tree, as a directory config/<name> containing
all of the required header files.

The mechanism also allows for users to define multiple local
configurations, by creating header files in the directory
config/local/<name>.

Note that the config/*.h files which are used only to configure
internal iPXE APIs (e.g. config/ioapi.h) cannot be modified via a
named configuration.  This avoids rebuilding the entire iPXE codebase
whenever switching to a different named configuration.

Inspired-by: Robin Smidsrød <robin@smidsrod.no>
Tested-by: Robin Smidsrød <robin@smidsrod.no>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

Move VMWARE_SETTINGS build configuration option from config/sideband.h
to a new config/settings.h.

Existing instances of config/local/sideband.h will not be affected,
since config.c still #includes config/sideband.h.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Allow iPXE settings to be specified in the .vmx file via the VMware
GuestInfo mechanism.  For example:

    guestinfo.ipxe.filename = "http://boot.ipxe.org/demo/boot.php"
    guestinfo.ipxe.dns = "192.168.0.1"
    guestinfo.ipxe.net0.ip = "192.168.0.15"
    guestinfo.ipxe.net0.netmask = "255.255.255.0"
    guestinfo.ipxe.net0.gateway = "192.168.0.1"

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Signed-off-by: Michael Brown <mcb30@ipxe.org>