Fix ebuild file and src code for cross compilation.

1. Fix dependency check (use compiler preprocessor instead of checking path existence).
2. Use flags like $(CC), etc. for cross compilation.
3. Remove inline for clang linker to find definition (compiler unfolds leaf function as optimizations).
4. Allow parallel compilation.

--- a/makefile
+++ b/makefile
@@ -11,11 +11,11 @@ LIBS=-ldl
 endif
 
 define dependencies
-@if [ ! -e /usr/include/cups ]; then echo "CUPS headers not available - exiting"; exit 1; fi
+@if ! echo '#include <cups/cups.h>' | $(CC) $(CPPFLAGS) -E ->/dev/null 2>&1; then echo "CUPS headers not available - exiting"; exit 1; fi
 endef
 
 define init
-@if [ ! -e bin ]; then echo "mkdir bin"; mkdir bin; fi
+@if [ ! -e bin ]; then echo "mkdir bin"; mkdir -p bin; fi
 endef
 
 define sweep
@@ -66,16 +66,17 @@ rastertostar: rastertostar.c
 	$(dependencies)
 	$(init)
 	# compiling rastertostar filter
-	gcc -Wl,-rpath,/usr/lib -Wall -fPIC -O2 $(DEFS) -o bin/rastertostar src/rastertostar.c $(LIBS)
+	$(CC) -Wall $(DEFS) $(CPPFLAGS) $(CFLAGS) -fPIC $(LDFLAGS) -o bin/rastertostar src/rastertostar.c $(LIBS)
 
 rastertostarlm: rastertostarlm.c
 	$(dependencies)
 	$(init)
 	# compiling rastertostarlm filter
-	gcc -Wl,-rpath,/usr/lib -Wall -fPIC -O2 $(DEFS) -o bin/rastertostarlm src/rastertostarlm.c $(LIBS)
+	$(CC) -Wall $(DEFS) $(CPPFLAGS) $(CFLAGS) -fPIC $(LDFLAGS) -o bin/rastertostarlm src/rastertostarlm.c $(LIBS)
 
 
 $(ppds): %.ppd.gz: %.ppd
+	$(init)
 	# gzip ppd file
 	gzip -c $< >> bin/$@
 
--- a/src/rastertostar.c
+++ b/src/rastertostar.c
@@ -636,7 +636,7 @@ static const struct command endJobCommand =
 static const struct command yRelCommand =
 {9,(char[9]){0x1b,'*','r','Y','x','x','x','x',0x00}};
 
-inline void debugPrintSettings(struct settings_ * settings)
+void debugPrintSettings(struct settings_ * settings)
 {
   fprintf(stderr, "DEBUG: pageType = %d\n"    , settings->pageType);
   fprintf(stderr, "DEBUG: focusArea = %d\n"   , settings->focusArea);
@@ -670,7 +670,7 @@ inline void debugPrintSettings(struct settings_ * settings)
   fprintf(stderr, "DEBUG: dataTreatmentRecoverFromError = %d\n", settings->dataTreatmentRecoverFromError);
 }
 
-inline void outputCommand(struct command output)
+void outputCommand(struct command output)
 {
     int i = 0;
 
@@ -680,17 +680,17 @@ inline void outputCommand(struct command output)
     }
 }
 
-inline void outputAsciiEncodedLength(int length)
+void outputAsciiEncodedLength(int length)
 {
     printf("%d",length);
 }
 
-inline void outputNullTerminator()
+void outputNullTerminator()
 {
     putchar(0x00);
 }
 
-inline int getOptionChoiceIndex(const char * choiceName, ppd_file_t * ppd)
+int getOptionChoiceIndex(const char * choiceName, ppd_file_t * ppd)
 {
     ppd_choice_t * choice;
     ppd_option_t * option;
@@ -705,7 +705,7 @@ inline int getOptionChoiceIndex(const char * choiceName, ppd_file_t * ppd)
     return atoi(choice->choice);
 }
 
-inline void getPageWidthPageHeight(ppd_file_t * ppd, struct settings_ * settings)
+void getPageWidthPageHeight(ppd_file_t * ppd, struct settings_ * settings)
 {
     ppd_choice_t * choice;
     ppd_option_t * option;
@@ -819,7 +819,7 @@ inline void getPageWidthPageHeight(ppd_file_t * ppd, struct settings_ * settings
     }
 }
 
-inline void initializeSettings(char * commandLineOptionSettings, struct settings_ * settings)
+void initializeSettings(char * commandLineOptionSettings, struct settings_ * settings)
 {
     ppd_file_t *    ppd         = NULL;
     cups_option_t * options     = NULL;
--- a/src/rastertostarlm.c
+++ b/src/rastertostarlm.c
@@ -447,7 +447,7 @@ static const struct command docCutTypeCommand [4] =
 static const struct command yRelCommand =
 {3,(char[3]){0x1b,'I','x'}};
 
-inline void outputCommand(struct command output)
+void outputCommand(struct command output)
 {
     int i = 0;
 
@@ -457,17 +457,17 @@ inline void outputCommand(struct command output)
     }
 }
 
-inline void outputAsciiEncodedLength(int length)
+void outputAsciiEncodedLength(int length)
 {
     printf("%d",length);
 }
 
-inline void outputNullTerminator()
+void outputNullTerminator()
 {
     putchar(0x00);
 }
 
-inline int getOptionChoiceIndex(const char * choiceName, ppd_file_t * ppd)
+int getOptionChoiceIndex(const char * choiceName, ppd_file_t * ppd)
 {
     ppd_choice_t * choice;
     ppd_option_t * option;
@@ -484,7 +484,7 @@ inline int getOptionChoiceIndex(const char * choiceName, ppd_file_t * ppd)
     return atoi(choice->choice);
 }
 
-inline void getPageWidthPageHeight(ppd_file_t * ppd, struct settings_ * settings)
+void getPageWidthPageHeight(ppd_file_t * ppd, struct settings_ * settings)
 {
     ppd_choice_t * choice;
     ppd_option_t * option;
@@ -598,7 +598,7 @@ inline void getPageWidthPageHeight(ppd_file_t * ppd, struct settings_ * settings
     }
 }
 
-inline void initializeSettings(char * commandLineOptionSettings, struct settings_ * settings)
+void initializeSettings(char * commandLineOptionSettings, struct settings_ * settings)
 {
     ppd_file_t *    ppd         = NULL;
     cups_option_t * options     = NULL;