add support for '@' parameters

add support for '@' parameters

These indicate to the compiler that additional command line options
should be read from a text file. If encountered, read the file,
tokenize any arguments, and if any are found, do an in-place replacement
of the '@' parameter with the arguments within the file.

args_insert() added to insert a set of arguments into a position within
another set of arguments.

args_init_from_string() has been improved so that any character may be
included by prefixing that character with a backslash, and support for
quoted arguments which pass special characters within the quotation marks
unmodified.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>