Avoid using the term "file" and prefer "url" in some docs and comments

This should make it less ambigous that these are URLs
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

doc/ffmpeg.texi

@@ -12,7 +12,7 @@
 
 @chapter Synopsis
 
-ffmpeg [@var{global_options}] @{[@var{input_file_options}] -i @file{input_file}@} ... @{[@var{output_file_options}] @file{output_file}@} ...
+ffmpeg [@var{global_options}] @{[@var{input_file_options}] -i @file{input_url}@} ... @{[@var{output_file_options}] @file{output_url}@} ...
 
 @chapter Description
 @c man begin DESCRIPTION
@@ -24,10 +24,10 @@ rates and resize video on the fly with a high quality polyphase filter.
 @command{ffmpeg} reads from an arbitrary number of input "files" (which can be regular
 files, pipes, network streams, grabbing devices, etc.), specified by the
 @code{-i} option, and writes to an arbitrary number of output "files", which are
-specified by a plain output filename. Anything found on the command line which
-cannot be interpreted as an option is considered to be an output filename.
+specified by a plain output url. Anything found on the command line which
+cannot be interpreted as an option is considered to be an output url.
 
-Each input or output file can, in principle, contain any number of streams of
+Each input or output url can, in principle, contain any number of streams of
 different types (video/audio/subtitle/attachment/data). The allowed number and/or
 types of streams may be limited by the container format. Selecting which
 streams from which inputs will go into which output is either done automatically
@@ -243,8 +243,8 @@ Force input or output file format. The format is normally auto detected for inpu
 files and guessed from the file extension for output files, so this option is not
 needed in most cases.
 
-@item -i @var{filename} (@emph{input})
-input file name
+@item -i @var{url} (@emph{input})
+input file url
 
 @item -y (@emph{global})
 Overwrite output files without asking.
@@ -281,7 +281,7 @@ libx264, and the 138th audio, which will be encoded with libvorbis.
 When used as an input option (before @code{-i}), limit the @var{duration} of
 data read from the input file.
 
-When used as an output option (before an output filename), stop writing the
+When used as an output option (before an output url), stop writing the
 output after its duration reaches @var{duration}.
 
 @var{duration} must be a time duration specification,
@@ -310,7 +310,7 @@ extra segment between the seek point and @var{position} will be decoded and
 discarded. When doing stream copy or when @option{-noaccurate_seek} is used, it
 will be preserved.
 
-When used as an output option (before an output filename), decodes but discards
+When used as an output option (before an output url), decodes but discards
 input until the timestamps reach @var{position}.
 
 @var{position} must be a time duration specification,
@@ -1168,7 +1168,7 @@ may be reassigned to a different value.
 For example, to set the stream 0 PID to 33 and the stream 1 PID to 36 for
 an output mpegts file:
 @example
-ffmpeg -i infile -streamid 0:33 -streamid 1:36 out.ts
+ffmpeg -i inurl -streamid 0:33 -streamid 1:36 out.ts
 @end example
 
 @item -bsf[:@var{stream_specifier}] @var{bitstream_filters} (@emph{output,per-stream})

doc/ffplay.texi

@@ -12,7 +12,7 @@
 
 @chapter Synopsis
 
-ffplay [@var{options}] [@file{input_file}]
+ffplay [@var{options}] [@file{input_url}]
 
 @chapter Description
 @c man begin DESCRIPTION
@@ -106,8 +106,8 @@ the input audio.
 Use the option "-filters" to show all the available filters (including
 sources and sinks).
 
-@item -i @var{input_file}
-Read @var{input_file}.
+@item -i @var{input_url}
+Read @var{input_url}.
 @end table
 
 @section Advanced options

doc/ffprobe.texi

@@ -12,7 +12,7 @@
 
 @chapter Synopsis
 
-ffprobe [@var{options}] [@file{input_file}]
+ffprobe [@var{options}] [@file{input_url}]
 
 @chapter Description
 @c man begin DESCRIPTION
@@ -24,8 +24,8 @@ For example it can be used to check the format of the container used
 by a multimedia stream and the format and type of each media stream
 contained in it.
 
-If a filename is specified in input, ffprobe will try to open and
-probe the file content. If the file cannot be opened or recognized as
+If a url is specified in input, ffprobe will try to open and
+probe the url content. If the url cannot be opened or recognized as
 a multimedia file, a positive exit code is returned.
 
 ffprobe may be employed both as a standalone application or in
@@ -332,8 +332,8 @@ with name "PIXEL_FORMAT".
 Force bitexact output, useful to produce output which is not dependent
 on the specific build.
 
-@item -i @var{input_file}
-Read @var{input_file}.
+@item -i @var{input_url}
+Read @var{input_url}.
 
 @end table
 @c man end

ffmpeg_opt.c

@@ -3195,8 +3195,8 @@ enum OptGroup {
 };
 
 static const OptionGroupDef groups[] = {
-    [GROUP_OUTFILE] = { "output file",  NULL, OPT_OUTPUT },
-    [GROUP_INFILE]  = { "input file",   "i",  OPT_INPUT },
+    [GROUP_OUTFILE] = { "output url",  NULL, OPT_OUTPUT },
+    [GROUP_INFILE]  = { "input url",   "i",  OPT_INPUT },
 };
 
 static int open_files(OptionGroupList *l, const char *inout,