Add detailed log() and assert() functions

In order to easy debug, this patch makes detailed log() and assert()
functions when 'CONFIG_DEBUG' is defined. For example, CPPFLAGS has
'-DCONFIG_DEBUG', log message shows you its file name and line number.
This patch also overrides glibc assert() for adding detailed message.

Signed-off-by: Sangjung Woo <sangjung.woo@samsung.com>
Enable log() and assert() functions

In order to easy debug, log() and assert() functions are applied to
bootchart-collector codes that is written in C language. For example,
CPPFLAGS has '-DCONFIG_DEBUG', log message shows you its file name and
line number. Without 'CONFIG_DEBUG' options, the result is the same as
before.

Signed-off-by: Sangjung Woo <sangjung.woo@samsung.com>
Clean up warning messages when compiling

This patch cleans up below warning messages. Most of them are related
with _unchecking_ the return value.

- collector/collector.c:445:14: warning: variable 'rc' set but not used
- collector/dump.c:483:10: warning: ignoring result value of 'fgets',
  declared with attribute warn_unused_result
- collector/dump.c:199:8: warning: ignoring result value of 'chdir',
  declared with attribute warn_unused_result
- collector/collector.c:641:11: warning: ignoring result value of
  'freopen', declared with attribute warn_unused_result
- collector/collector.c:559:8: warning: ignoring result value of
  'fgets', declared with attribute warn_unused_result

Signed-off-by: Sangjung Woo <sangjung.woo@samsung.com>