oxcmail: read /etc/mime.types for obtaining more MIME type-extension …

…pairs

For example, png is absent from data/mime_extension.txt.

lib/textmaps.cpp

@@ -260,6 +260,7 @@ void textmaps_init(const char *datapath)
 		mlog(LV_INFO, "textmaps: lang_charset: %zu mappings",
 		        g_lang2cset_map.size());
 		smap_read("mime_extension.txt", datapath, g_ext2mime_map, g_mime2ext_map);
+		smap_read("/etc/mime.types", datapath, g_mime2ext_map, g_ext2mime_map);
 		mlog(LV_INFO, "textmaps: mime_extension: %zu exts, %zu mimetypes",
 		        g_ext2mime_map.size(), g_mime2ext_map.size());
 		folder_namedb_read("folder_names.txt", datapath, folder_name_map);