fs/Path: rename GetSuffix() to GetExtension()

The "extension" is the name after the dot, but the "suffix" is the
string including the dot.

src/fs/AllocatedPath.hxx

@@ -296,8 +296,8 @@ public:
 	}
 
 	[[gnu::pure]]
-	const_pointer GetSuffix() const noexcept {
-		return Path{*this}.GetSuffix();
+	const_pointer GetExtension() const noexcept {
+		return Path{*this}.GetExtension();
 	}
 
 	/**

src/fs/Path.cxx

@@ -37,7 +37,7 @@ Path::ToUTF8Throw() const
 }
 
 Path::const_pointer
-Path::GetSuffix() const noexcept
+Path::GetExtension() const noexcept
 {
 	const auto base = GetBase().c_str();
 	const auto *dot = StringFindLast(base, '.');

src/fs/Path.hxx

@@ -167,7 +167,7 @@ public:
 	}
 
 	[[gnu::pure]]
-	const_pointer GetSuffix() const noexcept;
+	const_pointer GetExtension() const noexcept;
 };
 
 /**