Fix compilation errors/warning with gcc-5.4.0 (#137)

Warning are like this:
 error: ‘delimiter’ may be used uninitialized in this function [-Werror=maybe-uninitialized]

server/core/buffer.c

@@ -526,8 +526,8 @@ int gwbuf_compare(const GWBUF* lhs, const GWBUF* rhs)
 
             while ((rv == 0) && (i < llen))
             {
-                uint8_t lc;
-                uint8_t rc;
+                uint8_t lc = 0;
+                uint8_t rc = 0;
 
                 ss_debug(bool rv1 = ) gwbuf_get_byte(&lhs, &loffset, &lc);
                 ss_debug(bool rv2 = ) gwbuf_get_byte(&rhs, &roffset, &rc);

server/core/externcmd.c

@@ -37,7 +37,7 @@ int tokenize_arguments(char* argstr, char** argv)
     bool escaped = false;
     char *ptr, *start;
     char args[strlen(argstr) + 1];
-    char qc;
+    char qc = 0;
 
     strcpy(args, argstr);
     start = args;

server/core/log_manager.cc

@@ -751,11 +751,11 @@ static int logmanager_write_log(int            priority,
                                 size_t         str_len,
                                 const char*    str)
 {
-    logfile_t*   lf;
-    char*        wp;
+    logfile_t*   lf = NULL;
+    char*        wp = NULL;
     int          err = 0;
-    blockbuf_t*  bb;
-    blockbuf_t*  bb_c;
+    blockbuf_t*  bb = NULL;
+    blockbuf_t*  bb_c = NULL;
     size_t       timestamp_len;
     int          i;
 

server/core/modutil.c

@@ -797,7 +797,7 @@ char* strnchr_esc(char* ptr, char c, int len)
     char* p = (char*)ptr;
     char* start = p;
     bool quoted = false, escaped = false;
-    char qc;
+    char qc = 0;
 
     while (p < start + len)
     {
@@ -843,7 +843,7 @@ char* strnchr_esc_mysql(char* ptr, char c, int len)
     char* p = (char*) ptr;
     char* start = p, *end = start + len;
     bool quoted = false, escaped = false, backtick = false, comment = false;
-    char qc;
+    char qc = 0;
 
     while (p < end)
     {

server/core/poll.c

@@ -1256,7 +1256,7 @@ void
 dShowThreads(DCB *dcb)
 {
     int i, j, n;
-    char *state;
+    char *state = NULL;
     double avg1 = 0.0, avg5 = 0.0, avg15 = 0.0;
     double qavg1 = 0.0, qavg5 = 0.0, qavg15 = 0.0;
 

server/core/server.c

@@ -941,9 +941,9 @@ serverRowCallback(RESULTSET *set, void *data)
 {
     int *rowno = (int *)data;
     int i = 0;
-    char *stat, buf[20];
-    RESULT_ROW *row;
-    SERVER *server;
+    char *stat = NULL, buf[20];
+    RESULT_ROW *row = NULL;
+    SERVER *server = NULL;
 
     spinlock_acquire(&server_spin);
     server = allServers;

server/core/service.c

@@ -1210,8 +1210,8 @@ void serviceSetRetryOnFailure(SERVICE *service, char* value)
 bool
 serviceSetFilters(SERVICE *service, char *filters)
 {
-    MXS_FILTER_DEF **flist;
-    char *ptr, *brkt;
+    MXS_FILTER_DEF **flist = NULL;
+    char *ptr = NULL, *brkt = NULL;
     int n = 0;
     bool rval = true;
     uint64_t capabilities = 0;

server/core/utils.c

@@ -957,7 +957,7 @@ int open_network_socket(enum mxs_socket_type type, struct sockaddr_storage *addr
     ss_dassert(type == MXS_SOCKET_NETWORK || type == MXS_SOCKET_LISTENER);
 #ifdef __USE_POSIX
     struct addrinfo *ai = NULL, hint = {};
-    int so, rc;
+    int so = 0, rc = 0;
     hint.ai_socktype = SOCK_STREAM;
     hint.ai_family = AF_UNSPEC;
     hint.ai_flags = AI_ALL;