util/kconfig: New 'symbol' syntax

    * 'symbol' token added to the lexer and parser as T_SYMOPT
    * char *symopt added to the symbol structure
    * A new 'Qemu symbol' line added to the information text
      to make the following syntax usable:

    config TEST
        bool "This is a test example"
        symbol "TARGET_TEST"
        default n

Signed-off-by: Ákos Kovács <akoskovacs@gmx.com>
util/kconfig: *c_shipped files updated to the new symbol syntax

Signed-off-by: Ákos Kovács <akoskovacs@gmx.com>
Kconfig: Use the new symbol syntax

Signed-off-by: Ákos Kovács <akoskovacs@gmx.com>