Remove gcc warning due to missing prototype for 'testandset'

Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>

libpthread/linuxthreads.old/sysdeps/sh/pt-machine.h

@@ -29,6 +29,8 @@
 # define PT_EI __extern_always_inline
 #endif
 
+extern long int testandset (int *spinlock);
+
 /* Spinlock implementation; required.  */
 PT_EI long int
 testandset (int *spinlock)

libpthread/linuxthreads/sysdeps/sh/pt-machine.h

@@ -29,6 +29,8 @@
 # define PT_EI __extern_always_inline
 #endif
 
+extern long int testandset (int *spinlock);
+
 /* Spinlock implementation; required.  */
 PT_EI long int
 testandset (int *spinlock)