Renamed programmererror.c to errors.c so we can add internal errors (which used to be called implementation bugs).

common/meson.build

@@ -1,6 +1,6 @@
 # 23 march 2019
 
 libui_sources += [
+	'common/errors.c',
 	'common/init.c',
-	'common/programmererror.c',
 ]

common/uipriv.h

@@ -10,7 +10,7 @@ extern int uiprivSysInit(void *options, uiInitError *err);
 extern int uiprivInitReturnError(uiInitError *err, const char *msg);
 extern int uiprivInitReturnErrorf(uiInitError *err, const char *msg, ...);
 
-// programmererror.c
+// errors.c
 enum {
 	uiprivProgrammerErrorWrongStructSize,		// arguments: size_t badSize, const char *structName
 	uiprivProgrammerErrorIndexOutOfRange,	// arguments: int badIndex, __func__