package/ngrep: bump to version 1.47

package/ngrep: bump to version 1.47

- Switch site from sourceforge to github as there is no new releases on
  sourceforge and http://ngrep.sourceforge.net/ is redirected to
  https://github.com/jpr5/ngrep/
- Remove first patch, not needed since version 1.46 and
  https://github.com/jpr5/ngrep/commit/997c9d81d34d3a6646e6c5e363645015e644b3de
  as this commit added the support for system pcre
- Remove second patch, not needed since version 1.46 and
  https://github.com/jpr5/ngrep/commit/2d8fd9ac7ef1ac6947f738f6005e7b533654f331
- Remove third patch and LIBS=-lpcap -lpcre, not needed since 1.46 and
  https://github.com/jpr5/ngrep/commit/cca6e3121f2d80dd32a5a33dead9495fe40eed70
- LICENSE.txt has been renamed to LICENSE since version 1.47 and
  https://github.com/jpr5/ngrep/commit/3cb4c580a9de4afe11c2c17b0f354b59b74ae974
- Add an upstream patch to fix --enable-pcre: keep pcre as a mandatory
  dependency as this is the current behavior in version 1.45. PCRE will
  made optional in an other patch
- Remove --with-pcre which is not recognized anymore
- Add two other patches to fix --disable-tcpkill
- Add hash for license file

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>