gitweb: text files for 'blob_plain' action without charset by default
gitweb: text files for 'blob_plain' action without charset by default

$default_text_plain_charset is undefined (no specified charset) by
default. Additionally ':raw' layer for binmode is used for outputting file
content.

Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git