Fix sol-thread.c build failure.

Some updates where needed after the minimal symbol handling got changed
a little. This patch makes those changes.

gdb/ChangeLog:

        * sol-thread.c: #include "symtab.h", "minsym.h" and "objfiles.h".
        (ps_pglobal_lookup): Use BMSYMBOL_VALUE_ADDRESS instead of
        SYMBOL_VALUE_ADDRESS.
        (info_cb): MSYMBOL_PRINT_NAME instead of SYMBOL_PRINT_NAME.