Restrict allowed field names to avoid wrong matches

Only the English alphabet, - and _ are allowed in field names
in order to avoid erroneous detection in multi line contents.
13 jobs for master in 2 minutes and 32 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Test
passed bib-conva_test #26980

00:00:38

passed bib-convl_test #26981

00:00:46

passed bib-convu_test #26982

00:00:47

passed bib-extract_test #26983

00:01:30

passed bib-format_test #26984

00:00:44

passed bib-jabbr_test #26985

00:00:48

passed bib-keyinsert_test #26986

00:00:39

passed bib-name_test #26987

00:00:33

passed bib-order_test #26988

00:00:30

passed bib-pdfinsert_test #26989

00:00:36

passed bib-separate_test #26990

00:00:27

passed bib-txt_test #26991

00:00:28

passed bib-unite_test #26992

00:00:21