This patch makes gdb actually create breakpoints with
multiple locations. First, we use decode_line_1 to get
sal. After that, we try to find all PC values that correspond
to the same file:line as the original sal. Those new sals
are used for locations.

Some care is taken not to generate extra sals when not necessary:

	- When breakpoint is requested at address, we don't
	expand at all.
	- We never generate two sals with PC values in the same
	block, so that if scheduler scattered the line, we don't
	set breakpoints on all pieces of a line.

This patch includes testcases for constructors and templates. OK?

- Volodya