Please fix a bug in bb_mkdep.c.

[Vladimir N. Oleynik]

I wrote:

>> I want to move the USAGE_BLAH(x) macros from _usage.h to bb_config.h.  

> mkdep unsupport
> #if expr
> syntax

ftp://ftp.simtreas.ru/pub/my/bb/new
have bb_mkdep 4.0 version.

Changelog:

support for configs mode:

#if expression
#elif expression
#else
#endif

expression can have all knotty now: "defined"+-*/%!()<>=

#ifdef CONFIG_VAR
#ifndef CONFIG_VAR

save macros as is to config/features.h files after parse #if* true_conf_expr


--w
vodz