[IMM32] ImmCreateContext, ImmDestroyContext, DllMain etc. (#3867)

- Rewrite ImmCreateContext, ImmDestroyContext, and DllMain functions.
- Add g_hImm32Inst, g_bClientRegd, and g_SharedInfo global variables. Delete g_dwImm32Flags (that was g_psi->dwSRVIFlags).
- Implement ImmLoadIME and ImmRegisterClient functions.
- Modify CLIENTIMC and IMEDPI structures. Move CLIENTIMC definition into ntuser.h.
- Add file win32ss/include/imetable.h.
- Rename SRVINFO_METRICS macro as SRVINFO_CICERO_ENABLED.
CORE-11700

sdk/include/reactos/imm32_undoc.h

@@ -7,24 +7,6 @@
 
 #pragma once
 
-/* unconfirmed */
-typedef struct tagCLIENTIMC
-{
-    HIMC hImc;
-    LONG cLockObj;
-    DWORD dwFlags;
-    DWORD unknown;
-    RTL_CRITICAL_SECTION cs;
-    DWORD unknown2;
-    DWORD unknown3;
-    BOOL bUnknown4;
-} CLIENTIMC, *PCLIENTIMC;
-
-/* flags for CLIENTIMC */
-#define CLIENTIMC_WIDE 0x1
-#define CLIENTIMC_UNKNOWN1 0x40
-#define CLIENTIMC_UNKNOWN2 0x100
-
 #ifdef __cplusplus
 extern "C" {
 #endif