mke2fs: Escape double quotes when parsing mke2fs.conf

mke2fs: Escape double quotes when parsing mke2fs.conf

Currently, when constructing the <default> configuration pseudo-file using
the profile-to-c.awk script we will just pass the double quotes as they
appear in the mke2fs.conf.

This is problematic, because the resulting default_profile.c will either
fail to compile because of syntax error, or leave the resulting
configuration invalid.

It can be reproduced by adding the following line somewhere into
mke2fs.conf configuration and forcing mke2fs to use the <default>
configuration by specifying nonexistent mke2fs.conf

MKE2FS_CONFIG="nonexistent" ./misc/mke2fs -T ext4 /dev/device

default_mntopts = "acl,user_xattr"
^ this will fail to compile

default_mntopts = ""
^ this will result in invalid config file

Syntax error in mke2fs config file (<default>, line #4)
       Unknown code prof 17

Fix it by escaping the double quotes with a backslash in
profile-to-c.awk script.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>