yate: Revert to internal regex implementation

yate: Revert to internal regex implementation

.. because the musl implementation doesn't seem to be fully compatible
with yate. We switched to the musl implementation in f6ad95d.

Yate has this regexp:
^([[:alpha:]][[:alnum:]]+:)?/?/?([^[:space:][:cntrl:]@]+@)?([[:alnum:]._+-]+|[[][[:xdigit:].:]+[]])(:[0-9]+)?

Given a string like

  sip:012345678@11.111.11.111:5060;user=phone

musl's regexec() returns these matches:

index start end
0     -1    0
1     0     32   sip:012345678@11.111.11.111:5060
2     -1    -1
3     0     14   sip:012345678@
4     14    27   11.111.11.111
5     27    32   :5060

.. but this is what yate expects:

index start end
0     -1    0
1     0     32   sip:012345678@11.111.11.111:5060
2     0     4    sip:
3     4     14   012345678@
4     14    27   11.111.11.111
5     27    32   :5060

Fixes #378

Signed-off-by: Robert Högberg <robert.hogberg@gmail.com>