Add __bss16() macro, and allow use of .bss16 section by removing

link-time check for section overlaps.  (In order to avoid wasting
space in the executable image, .bss16 will overlap with the following
section, which is .text).

src/arch/i386/Config

 # this is almost always a win. the kernel uses it, too.
 CFLAGS+= -mpreferred-stack-boundary=2
 
-LDFLAGS+=	-N
+LDFLAGS+=	-N --no-check-sections
 
 ifeq "$(shell uname -s)" "FreeBSD"
 CFLAGS+=	-DIMAGE_FREEBSD -DELF_IMAGE -DAOUT_IMAGE

src/arch/i386/include/librm.h

 	__attribute__ (( section ( ".data16" ) ))			\
 	_data16_ ## variable array __asm__ ( #variable )
 
+#define __bss16( variable )						\
+	__attribute__ (( section ( ".bss16" ) ))			\
+	_data16_ ## variable __asm__ ( #variable )
+
+#define __bss16_array( variable, array )				\
+	__attribute__ (( section ( ".bss16" ) ))			\
+	_data16_ ## variable array __asm__ ( #variable )
+
 #define __text16( variable )						\
 	__attribute__ (( section ( ".text16.data" ) ))			\
 	_text16_ ## variable __asm__ ( #variable )