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, 15 insertions, 15 deletions

diff --git a/libnetdata/statistical/statistical.h b/libnetdata/statistical/statistical.h
index 9496e0e7f8..f3ecfadb46 100644
--- a/libnetdata/statistical/statistical.h
+++ b/libnetdata/statistical/statistical.h
@@ -5,30 +5,30 @@
 
 #include "../libnetdata.h"
 
-extern void log_series_to_stderr(NETDATA_DOUBLE *series, size_t entries, NETDATA_DOUBLE result, const char *msg);
+void log_series_to_stderr(NETDATA_DOUBLE *series, size_t entries, NETDATA_DOUBLE result, const char *msg);
 
-extern NETDATA_DOUBLE average(const NETDATA_DOUBLE *series, size_t entries);
-extern NETDATA_DOUBLE moving_average(const NETDATA_DOUBLE *series, size_t entries, size_t period);
-extern NETDATA_DOUBLE median(const NETDATA_DOUBLE *series, size_t entries);
-extern NETDATA_DOUBLE moving_median(const NETDATA_DOUBLE *series, size_t entries, size_t period);
-extern NETDATA_DOUBLE running_median_estimate(const NETDATA_DOUBLE *series, size_t entries);
-extern NETDATA_DOUBLE standard_deviation(const NETDATA_DOUBLE *series, size_t entries);
-extern NETDATA_DOUBLE single_exponential_smoothing(const NETDATA_DOUBLE *series, size_t entries, NETDATA_DOUBLE alpha);
+NETDATA_DOUBLE average(const NETDATA_DOUBLE *series, size_t entries);
+NETDATA_DOUBLE moving_average(const NETDATA_DOUBLE *series, size_t entries, size_t period);
+NETDATA_DOUBLE median(const NETDATA_DOUBLE *series, size_t entries);
+NETDATA_DOUBLE moving_median(const NETDATA_DOUBLE *series, size_t entries, size_t period);
+NETDATA_DOUBLE running_median_estimate(const NETDATA_DOUBLE *series, size_t entries);
+NETDATA_DOUBLE standard_deviation(const NETDATA_DOUBLE *series, size_t entries);
+NETDATA_DOUBLE single_exponential_smoothing(const NETDATA_DOUBLE *series, size_t entries, NETDATA_DOUBLE alpha);
 extern NETDATA_DOUBLE
 single_exponential_smoothing_reverse(const NETDATA_DOUBLE *series, size_t entries, NETDATA_DOUBLE alpha);
-extern NETDATA_DOUBLE double_exponential_smoothing(const NETDATA_DOUBLE *series, size_t entries,
+NETDATA_DOUBLE double_exponential_smoothing(const NETDATA_DOUBLE *series, size_t entries,
     NETDATA_DOUBLE alpha,
     NETDATA_DOUBLE beta,
     NETDATA_DOUBLE *forecast);
-extern NETDATA_DOUBLE holtwinters(const NETDATA_DOUBLE *series, size_t entries,
+NETDATA_DOUBLE holtwinters(const NETDATA_DOUBLE *series, size_t entries,
     NETDATA_DOUBLE alpha,
     NETDATA_DOUBLE beta,
     NETDATA_DOUBLE gamma,
     NETDATA_DOUBLE *forecast);
-extern NETDATA_DOUBLE sum_and_count(const NETDATA_DOUBLE *series, size_t entries, size_t *count);
-extern NETDATA_DOUBLE sum(const NETDATA_DOUBLE *series, size_t entries);
-extern NETDATA_DOUBLE median_on_sorted_series(const NETDATA_DOUBLE *series, size_t entries);
-extern NETDATA_DOUBLE *copy_series(const NETDATA_DOUBLE *series, size_t entries);
-extern void sort_series(NETDATA_DOUBLE *series, size_t entries);
+NETDATA_DOUBLE sum_and_count(const NETDATA_DOUBLE *series, size_t entries, size_t *count);
+NETDATA_DOUBLE sum(const NETDATA_DOUBLE *series, size_t entries);
+NETDATA_DOUBLE median_on_sorted_series(const NETDATA_DOUBLE *series, size_t entries);
+NETDATA_DOUBLE *copy_series(const NETDATA_DOUBLE *series, size_t entries);
+void sort_series(NETDATA_DOUBLE *series, size_t entries);
 
 #endif //NETDATA_STATISTICAL_H