perf tools: Provide subcmd configuration at runtime

Create init functions for exec_cmd.c and pager.c.  This allows their
configuration to be specified at runtime so they can be split out into a
separate library which can be used by other programs.  Their
configuration is stored in a shared subcmd_config struct.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/21f5f6b38da72c985a8dcfa185700d03e7eecd1d.1450193761.git.jpoimboe@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/Build b/tools/perf/Build
index 2a41217..00c4b8c 100644
--- a/tools/perf/Build
+++ b/tools/perf/Build
@@ -36,7 +36,10 @@
 
 CFLAGS_builtin-help.o      += $(paths)
 CFLAGS_builtin-timechart.o += $(paths)
-CFLAGS_perf.o              += -DPERF_HTML_PATH="BUILD_STR($(htmldir_SQ))" -include $(OUTPUT)PERF-VERSION-FILE
+CFLAGS_perf.o              += -DPERF_HTML_PATH="BUILD_STR($(htmldir_SQ))"	\
+			      -DPERF_EXEC_PATH="BUILD_STR($(perfexecdir_SQ))"	\
+			      -DPREFIX="BUILD_STR($(prefix_SQ))"		\
+			      -include $(OUTPUT)PERF-VERSION-FILE
 CFLAGS_builtin-trace.o	   += -DSTRACE_GROUPS_DIR="BUILD_STR($(STRACE_GROUPS_DIR_SQ))"
 
 libperf-y += util/