OS/KDrive/XFree86: Sanitise colour initialisation

OsInitColors always just returned TRUE, so just remove calls to it and
insane special-case logic.  Remove unused kcolor.c implementation, and
merge oscolor.h into oscolor.c since it was the only user.  Remove
open-coded strncasecmp in oscolor.c.

Since we no longer need to call OsInitColors after reading the config
file, just call PostConfigInit() from one place, and move PM handling to
one place so we can install the signal handlers earlier.

include/os.h

@@ -93,7 +93,6 @@ typedef struct _NewClientRec *NewClientPtr;
 #define SIGVAL void
 #endif
 
-extern Bool OsDelayInitColors;
 extern void (*OsVendorVErrorFProc)(const char *, va_list args);
 
 extern int WaitForSomething(
@@ -267,8 +266,6 @@ extern void OsVendorFatalError(void);
 
 extern void OsVendorInit(void);
 
-extern int OsInitColors(void);
-
 void OsBlockSignals (void);
 
 void OsReleaseSignals (void);