fix erlydtl compiling

Autorecompilation of erlydtl templates didn't work, at least in my environment.

If the template name is something like login.dtl it usually gets compiled by the erlydtl compiler to login_dtl.beam. Both erlang.mk and sync itself (determine_compile_fun_and_module_name function) do this name mangling this way.

But when sync tries to scan modules for source dirs it looks ".erl" in the module name for erlydtl templates, and as login.dtl does not contain any ".erl", get_src_dir_from_module function returns 'undefined'. As a result the directory is not included in the sources list.

WIth this fix it works as it should work.