Remove extern from function declared in headers. (#13790)

By default functions are declared as extern in C/C++ headers. The goal
of this PR is to reduce the wall of text that many headers have and,
more importantly, to make the declaration of extern'd variables - of
which we have many dispersed in various places - easily and quickly
identifiable.

Automatically generated with:

    $ git grep -l '^extern.*(' '**.h' | \
            grep -v libjudy | \
            grep -v 'sqlite3.h' | \
            xargs sed -i -e 's/extern \(.*(.*$\)/\1/'

This is a NFC.

1 files changed, 12 insertions, 12 deletions

diff --git a/libnetdata/threads/threads.h b/libnetdata/threads/threads.h
index 854503f315..ccc18aff0a 100644
--- a/libnetdata/threads/threads.h
+++ b/libnetdata/threads/threads.h
@@ -5,7 +5,7 @@
 
 #include "../libnetdata.h"
 
-extern pid_t gettid(void);
+pid_t gettid(void);
 
 typedef enum {
     NETDATA_THREAD_OPTION_DEFAULT          = 0 << 0,
@@ -21,27 +21,27 @@ typedef enum {
 typedef pthread_t netdata_thread_t;
 
 #define NETDATA_THREAD_TAG_MAX 100
-extern const char *netdata_thread_tag(void);
-extern int netdata_thread_tag_exists(void);
+const char *netdata_thread_tag(void);
+int netdata_thread_tag_exists(void);
 
-extern size_t netdata_threads_init(void);
-extern void netdata_threads_init_after_fork(size_t stacksize);
+size_t netdata_threads_init(void);
+void netdata_threads_init_after_fork(size_t stacksize);
 
-extern int netdata_thread_create(netdata_thread_t *thread, const char *tag, NETDATA_THREAD_OPTIONS options, void *(*start_routine) (void *), void *arg);
+int netdata_thread_create(netdata_thread_t *thread, const char *tag, NETDATA_THREAD_OPTIONS options, void *(*start_routine) (void *), void *arg);
 
 #ifdef NETDATA_INTERNAL_CHECKS
 #define netdata_thread_cancel(thread) netdata_thread_cancel_with_trace(thread, __LINE__, __FILE__, __FUNCTION__)
-extern int netdata_thread_cancel_with_trace(netdata_thread_t thread, int line, const char *file, const char *function);
+int netdata_thread_cancel_with_trace(netdata_thread_t thread, int line, const char *file, const char *function);
 #else
-extern int netdata_thread_cancel(netdata_thread_t thread);
+int netdata_thread_cancel(netdata_thread_t thread);
 #endif
 
-extern int netdata_thread_join(netdata_thread_t thread, void **retval);
-extern int netdata_thread_detach(pthread_t thread);
+int netdata_thread_join(netdata_thread_t thread, void **retval);
+int netdata_thread_detach(pthread_t thread);
 
 #define NETDATA_THREAD_NAME_MAX 15
-extern void uv_thread_set_name_np(uv_thread_t ut, const char* name);
-extern void os_thread_get_current_name_np(char threadname[NETDATA_THREAD_NAME_MAX + 1]);
+void uv_thread_set_name_np(uv_thread_t ut, const char* name);
+void os_thread_get_current_name_np(char threadname[NETDATA_THREAD_NAME_MAX + 1]);
 
 #define netdata_thread_self pthread_self
 #define netdata_thread_testcancel pthread_testcancel