Fixed/added missing/wrong function prototypes and made internal
functions static.

diff --git a/include/tapi.h b/include/tapi.h
index 4a80afa..f515249 100644
--- a/include/tapi.h
+++ b/include/tapi.h
@@ -601,6 +601,7 @@
 DWORD WINAPI phoneGetData(HPHONE,DWORD,LPVOID,DWORD);
 DWORD WINAPI phoneGetDevCaps(HPHONEAPP,DWORD,DWORD,DWORD,LPPHONECAPS);
 DWORD WINAPI phoneGetDisplay(HPHONE,LPVARSTRING);
+DWORD WINAPI phoneGetGain(HPHONE,DWORD,LPDWORD);
 DWORD WINAPI phoneGetHookSwitch(HPHONE,LPDWORD);
 DWORD WINAPI phoneGetID(HPHONE,LPVARSTRING,LPCSTR);
 DWORD WINAPI phoneGetIcon(DWORD,LPCSTR,HICON *);