Still further tweaking of s_lock assembler: do not assume that leading

Still further tweaking of s_lock assembler: do not assume that leading
whitespace is unimportant in assembly code.  Also, move VAX definition
of typedef slock_t to port header files to be like all the other ports.
Note that netbsd.h and openbsd.h are now identical, and I rather think
that freebsd.h is broken in the places where it doesn't agree --- but
I'll leave it to the freebsders to look at that.