BMessageFormat: Rename to BStringFormat.

The ICU class is named MessageFormat, but on Haiku, it sounds too much
like something related to BMessage (which it isn't in the slightest)
and not part of the Locale system. It works almost entirely with BStrings,
so naming it BStringFormat makes much more sense.

OK'ed by PulkoMandy and Humdinger.

headers/os/locale/StringFormat.h

@@ -6,8 +6,8 @@
  *		Adrien Destugues, pulkomandy@pulkomandy.tk
  *		John Scipione, jscipione@gmail.com
  */
-#ifndef _B_MESSAGE_FORMAT_H_
-#define _B_MESSAGE_FORMAT_H_
+#ifndef _B_STRING_FORMAT_H_
+#define _B_STRING_FORMAT_H_
 
 
 #include <Format.h>
@@ -22,12 +22,12 @@ namespace U_ICU_NAMESPACE {
 }
 
 
-class BMessageFormat: public BFormat {
+class BStringFormat : public BFormat {
 public:
-								BMessageFormat(const BLanguage& language,
+								BStringFormat(const BLanguage& language,
 									const BString pattern);
-								BMessageFormat(const BString pattern);
-								~BMessageFormat();
+								BStringFormat(const BString pattern);
+								~BStringFormat();
 
 			status_t			InitCheck();
 
@@ -41,4 +41,4 @@ private:
 };
 
 
-#endif	// _B_MESSAGE_FORMAT_H_
+#endif	// _B_STRING_FORMAT_H_