Do not trim spaces at the beginning in copyright header comment

[akihikodaki]

The copyright header rule trims spaces at the begginings of code comment lines. However, it does not perform the same operation for raw texts. That difference makes the rule think a code comment line and a raw text line different even if they are same. Such a raw text including a line beginning with spaces include Apache-2.0's copyright notice.

This change fixes the problem by removing the code trimming spaces. Additionally, this change takes spaces added when introducing new copyright headers into account.