Don't think so in on go...best I can think of is to read it with the first option and write that as a temporary file then process that file with the second.
I think textscan will only handle the case of '/*' '*/' pairs if they're first on the line, however, so perhaps you could get the same effect by reading the whole file as a char() array w/ fread, do a global substitution for strrep('/*','//') and then process that from memory?
Failing that, since one would presume c source files aren't terribly long, read line-by-line w/ fgetl and do the search on each line for either. This will let you get the end of line comments to as a side benefit to make up for the extra complexity...
ADDENDUM:
I reviewed the doc's for textscan; looks like it would catch the /* */ sequences correctly; what I recalled as beginning of line is actually written/documented as beginning of field.
