gcc 5 changed the default C standard which changes the behavior of extern
inline.  convert these tiny funcs to static inline to fix builds.

https://bugs.gentoo.org/568732

--- a/fdisk.h
+++ b/fdisk.h
@@ -224,12 +224,12 @@ extern jmp_buf listingbuf;
      :									\
      	(__var = (__typeof(__var))swab32((unsigned long)__var)))
 
-extern __inline__ unsigned short swab16( unsigned short val )
+static __inline__ unsigned short swab16( unsigned short val )
 {
     return( (val << 8) | (val >> 8) );
 }
 
-extern __inline__ unsigned long swab32( unsigned long val )
+static __inline__ unsigned long swab32( unsigned long val )
 {
     unsigned short vall = val, valh = val >> 16;
     vall = (vall << 8) | (vall >> 8);