Use default FindPerl CMake module and better documented sed dependency

CMakeLists.txt

@@ -40,6 +40,14 @@ project(Bro)
 set(PACKAGE "Bro")
 file(STRINGS "${CMAKE_SOURCE_DIR}/VERSION" VERSION LIMIT_COUNT 1)
 
+find_program(SED_EXE sed)
+if (NOT SED_EXE)
+    message(FATAL_ERROR "Could not find required dependency: sed")
+else ()
+    message(STATUS "Found sed: ${SED_EXE}")
+endif ()
+
+find_package(Perl REQUIRED)
 find_package(FLEX REQUIRED)
 find_package(BISON REQUIRED)
 find_package(PCAP REQUIRED)

INSTALL

@@ -15,6 +15,12 @@ before you begin with the installation:
        This comes with many systems, but if you get errors compiling
        parse.y, you will need to install it.
 
+    * Perl
+       Used only during the Bro build process
+
+    * sed
+       Used only during the Bro build process
+
     * BIND8 headers and libraries
        These are usually already installed as well.
 

src/CMakeLists.txt

@@ -1,18 +1,9 @@
-find_package(FLEX REQUIRED) 
-find_package(BISON REQUIRED)
-find_package(PCAP REQUIRED)
-
 include_directories(${CMAKE_CURRENT_SOURCE_DIR}
                     ${CMAKE_CURRENT_BINARY_DIR}
                     ${CMAKE_SOURCE_DIR}/binpac/lib
                     ${CMAKE_BINARY_DIR}/binpac/lib
                     )
 
-find_program(SED_EXE sed)
-if (NOT SED_EXE)
-    message(FATAL_ERROR "sed required")
-endif ()
-
 macro(REPLACE_YY_PREFIX_TARGET inFile outFile yylexPrefix yyPrefix)
     set(args "'/extern char.*getenv/d\;s/yylex/${yylexPrefix}lex/\;s/yy/${yyPrefix}/g'" < ${inFile} > ${outFile})
     add_custom_command(OUTPUT ${outFile}
@@ -198,14 +189,9 @@ if (USE_NMALLOC)
     set(malloc_SRCS malloc.c)
 endif ()
 
-find_program(PERL_EXE perl)
-if (NOT PERL_EXE)
-    message(FATAL_ERROR "perl required")
-endif ()
-
 add_custom_command(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/DebugCmdConstants.h
                           ${CMAKE_CURRENT_BINARY_DIR}/DebugCmdInfoConstants.h
-                   COMMAND ${PERL_EXE}
+                   COMMAND ${PERL_EXECUTABLE}
                    ARGS ${CMAKE_CURRENT_SOURCE_DIR}/make_dbg_constants.pl
                         ${CMAKE_CURRENT_SOURCE_DIR}/DebugCmdInfoConstants.in
                    DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/DebugCmdInfoConstants.in