Add the Unicode and Locale API files

Empty implementation files have also been added
Add the ICU headers to the libfoundation INCLUDE path
Add preliminary versions of the Unicode and Locale APIs
Add initial implementation of foundation-unicode

Not quite complete and still subject to API changes.
Plumb in the foundation-unicode stuff

The LiveCode engine is now linked against the libICU static libraries.
Move MCString*CString functions to libfoundation

After all, foundation-legacy should go away eventually...
Corrections to MCString*CString stuff

Libfoundation was the only part of the engine that declared MCStringCreateWithCString using a char_t* instead of char*.
Initial implementation of foundation-locale

Only includes the basic locale functionality. Does not yet to the date/time/number formatting extras.
Merge remote-tracking branch 'upstream/refactor-syntax_unicode' into refactor-syntax_unicode_libicu
Add number formatting support and basic calendar support
Expanded the date and calendar API

No implementation, yet.
Change the date/time API

The calendar and date formatter objects, along with the number formatter objects, have been moved into the locale object and are now accessed as part of the locale.
Initial plumbing-in of the ICU stuff

String searching (in most cases) and comparisons now use the ICU-provided string methods.
Change MCString{Lower,Upper}case to take a LocaleRef

Casing is a locale-dependent operation.
Expand number <-> character conversion options

The following functions have been added: numToNativeChar, numToUnicodeChar, nativeCharToNum, unicodeCharToNum.

The existing numToChar and charToNum functions pick the appropriate form based on the Unicodeness of the context.
Fixes to numToChar/charToNum

Unlike the new native/unicode functions, these need to maintain the old and slightly broken behaviour for backwards compatibility.
Merge remote-tracking branch 'upstream/refactor-syntax_unicode' into refactor-syntax_unicode_libicu

Conflicts:
	engine/src/util.cpp
Merge remote-tracking branch 'upstream/refactor-syntax_unicode' into refactor-syntax_unicode_libicu
Use ICU for some string search/replace calls

MCStringFirstIndexOf and MCStringFindAndReplaceChar
More ICU-ification of string searching

MCStringFindFirstIndexOfChar and MCStringFindLastIndexOfChar