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