* solib.c (solib_absolute_prefix): Delete. Replace
all uses with gdb_sysroot.
(_initialize_solib): Add "set sysroot" and "show sysroot".
Make "solib-absolute-prefix" an alias to it.
* gdb.texinfo (Commands to specify files): Describe
"set sysroot" and "show sysroot".
(Using the `gdbserver' program): Lowercase argument
to @var. Expand description of setting up GDB on the
host.