lib: whitespace cleanup

lib: whitespace cleanup

Cleaned the following whitespace in lib/* files:

lib/index.cc:              1 line:  trailing whitespace
lib/database.cc            5 lines: 8 spaces at the beginning of line
lib/notmuch-private.h:     4 lines: 8 spaces at the beginning of line
lib/message.cc:            1 line:  trailing whitespace
lib/sha1.c:                1 line:  empty lines at the end of file
lib/query.cc:              2 lines: 8 spaces at the beginning of line
lib/gen-version-script.sh: 1 line:  trailing whitespace