Add a note about default ports range and how it can be adjusted if necessary.
Add a note about default ports range and how it can be adjusted if necessary.

Submitted by:	Greger V. Teigre
BUG:		SER-45

Move Linux from the "known it compiles on" to the "has been extensively tested
on" league to make documentation matching the reality.

miconda/rtpproxy,dsanders11/rtpproxy,Vocalocity/rtpproxy-pre,jevonearth/rtpproxy,Vocalocity/rtpproxy-pre,jevonearth/rtpproxy,viraptor/RTPproxy,kiryu/rtpproxy,synety-jdebp/rtpproxy,dsanders11/rtpproxy,synety-jdebp/rtpproxy,kiryu/rtpproxy,Vocalocity/rtpproxy-pre,DrumTechnologiesLtd/rtpproxy,gtkiller/rtpproxyd,kiryu/rtpproxy,DrumTechnologiesLtd/rtpproxy,sippy/rtpproxy,DrumTechnologiesLtd/rtpproxy,mab-netdev/rtpproxy,hongbinz/rtpproxy,Vocalocity/rtpproxy-pre,hongbinz/rtpproxy,synety-jdebp/rtpproxy,sippy/rtpproxy,miconda/rtpproxy,hongbinz/rtpproxy,mab-netdev/rtpproxy,gtkiller/rtpproxyd,sippy/rtpproxy,jevonearth/rtpproxy,hongbinz/rtpproxy,miconda/rtpproxy,viraptor/RTPproxy,jevonearth/rtpproxy,dsanders11/rtpproxy,mab-netdev/rtpproxy,synety-jdebp/rtpproxy