TT#55204 Support building against mariadb 10.3.13

Instead of hardcoding -I/usr/include/mysql for CFLAGS and -lmysqlclient
for LDFLAGS, let's use mariadb_config if available (e.g. on
Debian/buster), try mysql_config otherwise (e.g. on Debian/stretch) or
if neither of them is available, fallback to -I/usr/include/mysql +
-lmysqlclient.

No longer include `m_string.h`, it was moved towards
/usr/include/mariadb/server/m_string.h and is no longer compatible when
used as such:

| /usr/include/mariadb/server/m_string.h:89:23: error: unknown type name 'uchar'; did you mean 'char'?
|  extern void bmove_upp(uchar *dst,const uchar *src,size_t len);

Also no longer use libmysqlclient15-dev as alternative Build-Depend,
it's not available in neither stretch nor buster.

While at it drop include for my_global.h, since it shouldn't be included
anymore (and it doesn't seem to be relevant for us, compiling fine as-is
on Debian/stretch and Debian/buster):

| /usr/include/mariadb/my_global.h:3:2: warning: #warning This file should not be included by clients, include only <mysql.h> [-Wcpp]

Change-Id: I74a75ea24f72880adb8117ae5808095f03bc0edb

Makefile

@@ -7,14 +7,29 @@ CC := gcc
 CPPFLAGS := -DMEDIATOR_VERSION="\"$(VERSION)\""
 
 GLIB_CFLAGS := $(shell pkg-config glib-2.0 --cflags)
-CFLAGS := -I/usr/include/mysql $(GLIB_CFLAGS) -g -Wall -Wextra -O2 -D_GNU_SOURCE
+
+# mariadb/mysql support
+ifneq ($(shell which mariadb_config),)
+MYSQL_CFLAGS := $(shell mariadb_config --cflags)
+MYSQL_LDFLAGS := $(shell mariadb_config --libs)
+else ifneq ($(shell which mysql_config),)
+MYSQL_CFLAGS := $(shell mysql_config --cflags)
+MYSQL_LDFLAGS := $(shell mysql_config --libs)
+else
+MYSQL_CFLAGS := -I/usr/include/mysql
+MYSQL_LDFLAGS := -lmysqlclient
+endif
+
+CFLAGS := $(GLIB_CFLAGS) -g -Wall -Wextra -O2 -D_GNU_SOURCE
+CFLAGS += $(MYSQL_CFLAGS)
 #CFLAGS += -DWITH_TIME_CALC
 CFLAGS += $(shell pkg-config json-c --cflags)
 CFLAGS += $(shell pkg-config hiredis --cflags)
 CFLAGS += $(shell pkg-config libsystemd --cflags)
 
 GLIB_LDFLAGS := $(shell pkg-config glib-2.0 --libs)
-LDFLAGS := $(GLIB_LDFLAGS) -lmysqlclient
+LDFLAGS := $(GLIB_LDFLAGS)
+LDFLAGS += $(MYSQL_LDFLAGS)
 LDFLAGS += $(shell pkg-config json-c --libs)
 LDFLAGS += $(shell pkg-config hiredis --libs)
 LDFLAGS += $(shell pkg-config libsystemd --libs)

debian/control

@@ -4,7 +4,7 @@ Priority: optional
 Maintainer: Sipwise Development Team <support@sipwise.com>
 Build-Depends:
  debhelper (>= 10),
- default-libmysqlclient-dev | libmysqlclient15-dev,
+ default-libmysqlclient-dev,
  libglib2.0-dev,
  libhiredis-dev,
  libjson-c-dev,

medmysql.c

@@ -1,5 +1,3 @@
-#include <my_global.h>
-#include <m_string.h>
 #include <mysql.h>
 #include <mysql/errmsg.h>
 #include <mysql/mysqld_error.h>