Rename most of the platform source files.

This gets rid of all those annoying 'win', 'ux' and 'gtk' prefixes
which made filenames annoying to type and to tab-complete. Also, as
with my other recent renaming sprees, I've taken the opportunity to
expand and clarify some of the names so that they're not such cryptic
abbreviations.

windows/cryptoapi.h

@@ -0,0 +1,27 @@
+/*
+ * cryptoapi.h: Windows Crypto API functions defined in PuTTY that
+ * use the crypt32 library. Also centralises the machinery for
+ * dynamically loading that library, and our own functions using that
+ * in turn.
+ */
+
+DECL_WINDOWS_FUNCTION(extern, BOOL, CryptProtectMemory, (LPVOID,DWORD,DWORD));
+
+bool got_crypt(void);
+
+/*
+ * Function to obfuscate an input string into something usable as a
+ * pathname for a Windows named pipe. Uses CryptProtectMemory to make
+ * the obfuscation depend on a key Windows stores for the owning user,
+ * and then hashes the string as well to make it have a manageable
+ * length and be composed of filename-legal characters.
+ *
+ * Rationale: Windows's named pipes all live in the same namespace, so
+ * one user can see what pipes another user has open. This is an
+ * undesirable privacy leak: in particular, if we used unobfuscated
+ * names for the connection-sharing pipe names, it would permit one
+ * user to know what username@host another user is SSHing to.
+ *
+ * The returned string is dynamically allocated.
+ */
+char *capi_obfuscate_string(const char *realname);