Adapt `info probes' to support printing probes of different types.

Adapt `info probes' to support printing probes of different types.

A "probe type" (backend for the probe abstraction implemented in
probe.[ch]) can extend the information printed by `info probes' by
defining additional columns.  This means that when `info probes' is
used to print all the probes regardless of their types, some of the
columns will be "not applicable" to some of the probes (like, say, the
Semaphore column only makes sense for SystemTap probes).  This patch
makes `info probes' fill these slots with "n/a" marks (currently it
breaks the table) and not include headers for which no actual probe
has been found in the list of defined probes.

This patch also adds support for a new generic column "Type", that
displays the type of each probe.  SystemTap probes identify themselves
as "stap" probes.

gdb/ChangeLog:

2015-02-17  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* probe.c (print_ui_out_not_applicables): New function.
	(exists_probe_with_pops): Likewise.
	(info_probes_for_ops): Do not include column headers for probe
	types for which no probe has been actually found on any object.
	Also invoke `print_ui_out_not_applicables' in order to match the
	column rows with the header when probes of several types are
	listed.
	Print the "Type" column.
	* probe.h (probe_ops): Added a new probe operation `type_name'.
	* stap-probe.c (stap_probe_ops): Add `stap_type_name'.
	(stap_type_name): New function.