Add the ability to set flags via the config options api

Add the ability to set flags via the config options api

Allows the setting of flags via the config options api.
For example, code like this:

#define OPT1 1 << 0
#define OPT2 1 << 1
#define OPT3 1 << 2

struct thing {
   unsigned int flags;
};

and a config like this:

[blah]
opt1=yes
opt2=no
opt3=yes

Review: https://reviewboard.asterisk.org/r/2004/

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@369454 65c4cc65-6c06-0410-ace0-fbb531ad65f3