perf/tool: Add support to reuse event grammar to parse out terms

We want to reuse the event grammar for parsing aliased terms.
The obvious reason is we dont need to add new code when there's
already support for this in event grammar.

Doing this by adding terms and event start entries into event
parse grammar. The grammar forks on the begining based on the
starting token, which is supplied via bison interface into the
lexer.  The lexer then returns the starting token as the first
token, thus making the grammar switch accordingly.

Currently 2 starting tokens/grammars are supported:

	PE_START_TERMS, PE_START_EVENTS

The PE_START_TERMS related grammar uses 'event_config' part
of the grammar for term parsing.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1339741902-8449-12-git-send-email-zheng.z.yan@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>