ENH: add the keywords OFFSET and HEX to the FILE() command, using OFFSET an

offset can be specified where the reading starts, and using HEX the data can
be converted into a hex string, so binary data can be compared with text
functions
-add docs for LIMIT, OFFSET and HEX

Alex

Source/cmFileCommand.h

@@ -68,7 +68,7 @@ public:
     return
       "  file(WRITE filename \"message to write\"... )\n"
       "  file(APPEND filename \"message to write\"... )\n"
-      "  file(READ filename variable [LIMIT numBytes])\n"
+      "  file(READ filename variable [LIMIT numBytes] [OFFSET offset] [HEX])\n"
       "  file(STRINGS filename variable [LIMIT_COUNT num]\n"
       "       [LIMIT_INPUT numBytes] [LIMIT_OUTPUT numBytes]\n"
       "       [LENGTH_MINIMUM numBytes] [LENGTH_MAXIMUM numBytes]\n"
@@ -93,7 +93,9 @@ public:
       "because it will lead to an infinite loop. Use configure_file if you "
       "want to generate input files to CMake.\n"
       "READ will read the content of a file and store it into the "
-      "variable.\n"
+      "variable. It will start at the given offset and read up to numBytes. "
+      "If the argument HEX is given, the binary data will be converted to "
+      "hexadecimal representation and this will be stored in the variable.\n"
       "STRINGS will parse a list of ASCII strings from a file and "
       "store it in a variable. Binary data in the file are ignored. Carriage "
       "return (CR) characters are ignored. It works also for Intel Hex and "