For SVR4 targets, enable gdb to set breakpoints in shared

	For SVR4 targets, enable gdb to set breakpoints in shared
	library functions before the executable is run.
	* elfread.c (elf_symtab_read):  Handle symbols for shared library
	functions.
	* sparc-tdep.c (in_solib_trampoline):  Renamed to in_plt_section
	and moved to objfiles.c.
	* objfiles.c (in_plt_section):  Moved to here from sparc-tdep.
	* config/tm-sysv4.h (IN_SOLIB_TRAMPOLINE):  Use new in_plt_section.
	* config/sparc/tm-sun4sol2.h (IN_SOLIB_TRAMPOLINE):  Removed,
	the new generic definition from tm-sysv4.h works for Solaris.