Document RELOLIS from commit 1bf58cf.

I hastily chose the name RELOLIS for this relocation type.  If we want
to rename it, we only need to edit these files:

 - h/out.h
 - mach/powerpc/as/mach5.c
 - util/amisc/ashow.c
 - util/led/ack.out.5
 - util/led/relocate.c

util/led/ack.out.5

@@ -166,6 +166,7 @@ struct outrelo {
 #define RELO2	0x02		/* 2 bytes */
 #define RELO4	0x03		/* 4 bytes */
 #define RELOPPC	0x04		/* 26-bit PowerPC address */
+#define RELOLIS	0x05		/* PowerPC lis */
 #define RELOVC4	0x06 /* VideoCore IV address in 32-bit insruction */
 #define RELPC	0x2000		/* pc relative */
 #define RELBR	0x4000		/* High order byte lowest address. */
@@ -225,10 +226,23 @@ is an absolute number, and the datum is relocated pc relative.
 The relocatable datum must then be relocated with respect to the
 base address of its section.
 .PP
+For RELOPPC and RELOVC4, the relocatable datum is a PowerPC or
+VideoCore IV instruction.
+The relocation depends on the instruction, and uses an offset encoded
+in the instruction.
+.PP
+RELOLIS assembles a PowerPC \fBlis\fR instruction.
+The relocatable datum is a 4-byte integer.
+The high bit is set for ha16 or clear for hi16.
+The next 5 bits are the register \fIRT\fR.
+The low 26 bits are a signed offset.
+The relocation replaces the datum with the PowerPC instruction
+\(oq\fBlis\fR\ \fIRT\fR,\ ha16[\fIsymbol\fR\ +\ \fIoffset\fR]\(cq.
+.PP
 .B The symbol table.
 .br
-This table contains definitions of symbols. It is referred to by
+This table contains definitions of symbols.
-outrelo-structures, and can be used by debuggers.
+It is referred to by outrelo-structures, and can be used by debuggers.
 Entries in this table have the following structure:
 .PP
 .nf