perf tools: Add variable display for VF make output

perf tools: Add variable display for VF make output

Adding dump of interesting build directories to the make VF=1 output.

  $ make VF=1
    BUILD:   Doing 'make -j4' parallel build

  Auto-detecting system features:
  ...                         dwarf: [ on  ]
  ...                         glibc: [ on  ]
  ...                          gtk2: [ on  ]
  ...                      libaudit: [ on  ]
  ...                        libbfd: [ on  ]
  ...                        libelf: [ on  ]
  ...                       libnuma: [ on  ]
  ...                       libperl: [ on  ]
  ...                     libpython: [ on  ]
  ...                      libslang: [ on  ]
  ...                     libunwind: [ on  ]
  ...                     backtrace: [ on  ]
  ...                fortify-source: [ on  ]
  ...                  gtk2-infobar: [ on  ]
  ...             libelf-getphdrnum: [ on  ]
  ...                   libelf-mmap: [ on  ]
  ...             libpython-version: [ on  ]
  ...                       on-exit: [ on  ]
  ...            stackprotector-all: [ on  ]
  ...                       timerfd: [ on  ]
  ...         libunwind-debug-frame: [ OFF ]
  ...                        bionic: [ OFF ]

  ...                        prefix: /home/jolsa
  ...                        bindir: /home/jolsa/bin
  ...                        libdir: /home/jolsa/lib64
  ...                    sysconfdir: /home/jolsa/etc

Adding functions to print variable/text in features display -
feature_print_var/feature_print_text (feature_print_text is used in next
patches).

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jean Pihet <jean.pihet@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1392825179-5228-3-git-send-email-jolsa@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>