lib/parse_ini.[ch]: Simplify code

Rewrite the code that looks up the INI configuration file path (used by
the Extra-Opts feature) in order to improve readability.  The behaviour
should not have changed.
lib/parse_ini.c: Read "monitoring-plugins.ini"

Read "monitoring-plugins.ini" if that file exists, but fall back to
reading "plugins.ini" or "nagios-plugins.ini" for backward
compatibility.
lib/parse_ini.c: Read $MP_CONFIG_FILE

Read $MP_CONFIG_FILE if that variable is set in the environment.
lib/parse_ini.c: Remove outdated comment and code

The lib/parse_ini.c:np_get_defaults() function now dies if no
configuration file is found.
lib/parse_ini.c: Don't cast malloc(3) result

There's no need to cast malloc(3)'s return value.
lib/parse_ini.[ch]: Change code formatting

Change the indentation and formatting of the code in lib/parse_ini.c.
This breaks patches against that file and makes it harder to track its
history, but it (hopefully) improves readability a lot.
lib/parse_ini.c: Fix Clang warnings
lib/parse_ini.c: Cosmetic changes to comments
lib/parse_ini.c: Add comment on NAGIOS_CONFIG_PATH

We might want to spit out a warning when NAGIOS_CONFIG_PATH is used.

While at it, move the function that handles this environment variable to
the bottom.
lib/parse_ini.c: Search for INI file in subdirs

Add two path names to the list of default INI file locations, as some
users/distributions prefer to put configuration files into
subdirectories.
plugins/runcmd.c: Remove superfluous newline

The puts(3) function already appends a newline character to the string.
Use FindBin consistently across Perl plugins

Use Perl's FindBin module to locate the path to utils.pm in
check_file_age.pl and check_mssql.pl, just as we do in other Perl
plugins.
Add Gnulib module "idpriv-droptemp"
lib/parse_ini.c: Cosmetic change

Replace an "if" with the ternary operator.
lib/parse_ini.c: Add newline to die() calls

Our die() function doesn't append a newline character to the message.
lib/parse_ini.c: Drop privileges for reading file

Read the configuration file with privileges temporarily dropped if the
code is used by a setuid plugin.
lib/parse_ini.c: Print proper read error message

Print a useful error message if opening the configuration file fails.
NEWS: s/MP_STATE_DIRECTORY/MP_STATE_PATH/

NAGIOS_PLUGIN_STATE_DIRECTORY was renamed to MP_STATE_PATH, not to
MP_STATE_DIRECTORY.
Add UID to state retention file path

Add the UID of the invoking user to the state retention file path.  This
helps solving permission issues when different users run the same
plugin.
REQUIREMENTS: Update radiusclient-ng URL

The project was moved to SourceForge.net.