apitrace: Parse comma-separated list in commandline

<b>Description</b>
In the command line argument list for --calls (and --frames), allow a
single comma-separated mixed list of files and/or ranges instead of
multiple option calls for each one.

E.g., instead of

    apitrace trim --calls=@foo.calls --calls=0-20 --calls=100-150 \
                  --calls=@goo.calls --calls=...

allow

    apitrace trim --calls=@foo.calls,0-20,100-150,@goo.calls,..

which is merged into one callset list of their union.

<b>Details</b>
CallSet class member function CallSet::merge() parses for comma-delimited
tokens in the input option string and adds them to the CallSet list

<b>Testing</b>
Tests have been added to the apitrace-tests repository.

Testing in apitrace-tests done on both
Linux: 3.14-1-amd64 #1 SMP Debian 3.14.4-1 (2014-05-13) x86_64 GNU/Linux
Windows 7: MINGW32_NT-6.1 1.0.12(0.46/3/2) 2012-07-05 14:56 i686 unknown

100% passing.

Signed-off-by: Lawrence L Love <lawrencex.l.love@intel.com>