[mpd] Add Bison/Flex parser for complex mpd commands + misc

Some of the misc:
* Initialize query_params from the start of each function
* Reduce code duplication by consolidating the handler's integer conversion
* Go back to classic int return types for handlers
* Change list grouping to respond like mpd
* Sanitize all user string output

src/Makefile.am

@@ -53,8 +53,8 @@ GPERF_FILES = \
 
 GPERF_SRC = $(GPERF_FILES:.gperf=_hash.h)
 
-LEXER_SRC  = parsers/daap_lexer.l parsers/smartpl_lexer.l parsers/rsp_lexer.l
-PARSER_SRC = parsers/daap_parser.y parsers/smartpl_parser.y parsers/rsp_parser.y
+LEXER_SRC  = parsers/daap_lexer.l parsers/smartpl_lexer.l parsers/rsp_lexer.l parsers/mpd_lexer.l
+PARSER_SRC = parsers/daap_parser.y parsers/smartpl_parser.y parsers/rsp_parser.y parsers/mpd_parser.y
 
 # This flag is given to Bison and tells it to produce headers. Note that
 # automake recognizes this flag too, and has special logic around it, so don't