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, 8 insertions, 8 deletions

diff --git a/libnetdata/procfile/procfile.h b/libnetdata/procfile/procfile.h
index 5263ad770c..5d45e4028c 100644
--- a/libnetdata/procfile/procfile.h
+++ b/libnetdata/procfile/procfile.h
@@ -60,25 +60,25 @@ typedef struct {
 } procfile;
 
 // close the proc file and free all related memory
-extern void procfile_close(procfile *ff);
+void procfile_close(procfile *ff);
 
 // (re)read and parse the proc file
-extern procfile *procfile_readall(procfile *ff);
+procfile *procfile_readall(procfile *ff);
 
 // open a /proc or /sys file
-extern procfile *procfile_open(const char *filename, const char *separators, uint32_t flags);
+procfile *procfile_open(const char *filename, const char *separators, uint32_t flags);
 
 // re-open a file
 // if separators == NULL, the last separators are used
-extern procfile *procfile_reopen(procfile *ff, const char *filename, const char *separators, uint32_t flags);
+procfile *procfile_reopen(procfile *ff, const char *filename, const char *separators, uint32_t flags);
 
 // example walk-through a procfile parsed file
-extern void procfile_print(procfile *ff);
+void procfile_print(procfile *ff);
 
-extern void procfile_set_quotes(procfile *ff, const char *quotes);
-extern void procfile_set_open_close(procfile *ff, const char *open, const char *close);
+void procfile_set_quotes(procfile *ff, const char *quotes);
+void procfile_set_open_close(procfile *ff, const char *open, const char *close);
 
-extern char *procfile_filename(procfile *ff);
+char *procfile_filename(procfile *ff);
 
 // ----------------------------------------------------------------------------