macOS: Add osx_getdocumentsdir

Needed because GOG .pkg installers default to the Documents folder

source/build/include/osxbits.h

@@ -20,6 +20,7 @@ char *osx_gethomedir(void);
 char *osx_getsupportdir(int32_t local);
 char *osx_getappdir(void);
 char *osx_getapplicationsdir(int32_t local);
+char *osx_getdocumentsdir(int32_t local);
 
 #ifdef __cplusplus
 }

source/build/src/osxbits.mm

@@ -177,3 +177,21 @@ char *osx_getapplicationsdir(int32_t local)
 
     return returnpath;
 }
+
+char *osx_getdocumentsdir(int32_t local)
+{
+    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, local ? NSUserDomainMask : NSLocalDomainMask, YES);
+    char *returnpath = NULL;
+
+    if ([paths count] > 0)
+    {
+        const char *Cpath = [[paths objectAtIndex:0] UTF8String];
+
+        if (Cpath)
+            returnpath = Bstrdup(Cpath);
+    }
+
+    [paths release];
+
+    return returnpath;
+}