add PBD::downcase() functions to libpbd

libs/pbd/convert.cc

@@ -18,6 +18,9 @@
 */
 
 #include <cmath>
+#include <algorithm>
+#include <string> 
+
 #include <stdint.h>
 #include <stdlib.h>
 #include <cstdio>
@@ -51,6 +54,24 @@ capitalize (const string& str)
         return ret;
 }
 
+string
+downcase (const string& str)
+{
+	string copy (str);
+	std::transform (copy.begin(), copy.end(), copy.begin(), ::tolower);
+	return copy;
+}
+
+const char*
+downcase (const char* str)
+{
+	char *copy = strdup (str);
+	for (char* p = copy; *p; ++p) {
+		*p = tolower (*p);
+	}
+	return copy;
+}
+
 string
 short_version (string orig, string::size_type target_length)
 {

libs/pbd/pbd/convert.h

@@ -40,6 +40,8 @@ LIBPBD_API double  atof (const std::string&);
 LIBPBD_API std::string url_decode (std::string const &);
 
 LIBPBD_API std::string capitalize (const std::string&);
+LIBPBD_API std::string downcase (const std::string&);
+LIBPBD_API const char* downcase (const char*);
 
 // std::string length2string (const int32_t frames, const float sample_rate);
 LIBPBD_API std::string length2string (const int64_t frames, const double sample_rate);