tcomment_types is ignored

[liuyang1]

my definition is:

let g:tcomment_types={'c': '// %s', 'asm': '# %s', 'gdb': '# %s'}

The config for 'C', is ignored.

I find this issue on eea1a7c version. The old version 952de7f is good.
I think this is a regression.