Fix: conflict between Raw64 and PlaintextNames flags in config

[monkberry71]

When creating a new volume with PlaintextNames enabled, the generated configuration file (gocryptfs.conf) incorrectly sets the Raw64 flag.
Raw64 (Base64 encoding for filenames) and PlaintextNames (no filename encryption) are mutually exclusive in gocryptfs, and enabling both causes compatibility issues.

The Issue (Before Fix)

Currently, creating a config with PlaintextNames results in the following conflicting flags:

// Generated by current version
{
	"Creator": "cppcryptfs v1.4.4.7",
	"EncryptedKey": "Z4Ao3yTqWZrCHFUs9Nuxy7Im2wAkvrD3MoNn1+p15xg9bWWz8cOrnxcgJlcABuqHhVw1/wJ1CZOD1F3YL2uSMA==",
	"ScryptObject": {
		"Salt": "7/GUVQtO+BbGXueekEZf1N6oNBxaxKMqrF5x57oF5Qk=",
		"N": 65536,
		"R": 8,
		"P": 1,
		"KeyLen": 32
	},
	"Version": 2,
	"VolumeName": "",
	"FsFeatureDisableMask": "00000",
	"FeatureFlags": [
		"PlaintextNames",
		"HKDF",
		"Raw64", <-- conflict
		"GCMIV128"
	]
}

gocryptfs --version
gocryptfs 2.4.0; go-fuse 2.4.2; 2025-06-24 go1.22.2 linux/amd64

gocryptfs . ~/test_win_mount
Cannot open config file: PlaintextNames conflicts with Raw64 feature flag

gocryptfs -info .
Loading config file failed: PlaintextNames conflicts with Raw64 feature flag

The Fix

I modified CryptConfig::create to explicitly disable the Raw64 flag when PlaintextNames is active. This ensures cppcryptfs generates configuration files that are compatible with gocryptfs validation rules.
I used m_PlaintextNames instead of the function argument to correctly respect the precedence logic (e.g., the EMENames check) defined earlier in the function.

Verification (After Fix)

After applying the fix, the generated configuration file is clean and correct:

// Generated with this PR
{
	"Creator": "cppcryptfs v1.4.4.7",
	"EncryptedKey": "QB+Z5YyAtRLv7KUitiOIQ1JmpdS0RYrIq5/njp7mP0p9W+VXawWPvRnALi8rXE2pV5OofktKggDz9b4B4+YTjA==",
	"ScryptObject": {
		"Salt": "D1pQ9UUU6bCnTP2UxSs3Zr0j0vq+w0Ho76ToxeRLlsA=",
		"N": 65536,
		"R": 8,
		"P": 1,
		"KeyLen": 32
	},
	"Version": 2,
	"VolumeName": "",
	"FsFeatureDisableMask": "00000",
	"FeatureFlags": [
		"PlaintextNames",
		"HKDF",
		"GCMIV128"
	] // "Raw64" is removed.
}

Verified that gocryptfs now recognizes and mounts the volume without errors.