Exclude flex-generated code from coverage testing

Flex generates a lot of functions that are not actually used.  In order
to avoid coverage figures being ruined by that, mark up the part of the
.l files where the generated code appears by lcov exclusion markers.
That way, lcov will typically only reported on coverage for the .l file,
which is under our control, but not for the .c file.

Reviewed-by: Michael Paquier <michael.paquier@gmail.com>

src/backend/bootstrap/bootscanner.l

@@ -38,6 +38,7 @@
 /* Not needed now that this file is compiled as part of bootparse. */
 /* #include "bootparse.h" */
 
+/* LCOV_EXCL_START */
 
 /* Avoid exit() on fatal scanner errors (a bit ugly -- see yy_fatal_error) */
 #undef fprintf
@@ -134,6 +135,8 @@ insert			{ return INSERT_TUPLE; }
 
 %%
 
+/* LCOV_EXCL_STOP */
+
 void
 yyerror(const char *message)
 {

src/backend/parser/scan.l

@@ -41,6 +41,9 @@
 }
 
 %{
+
+/* LCOV_EXCL_START */
+
 /* Avoid exit() on fatal scanner errors (a bit ugly -- see yy_fatal_error) */
 #undef fprintf
 #define fprintf(file, fmt, msg)  fprintf_to_ereport(fmt, msg)
@@ -1011,6 +1014,8 @@ other			.
 
 %%
 
+/* LCOV_EXCL_STOP */
+
 /*
  * Arrange access to yyextra for subroutines of the main yylex() function.
  * We expect each subroutine to have a yyscanner parameter.  Rather than

src/backend/replication/repl_scanner.l

@@ -38,6 +38,8 @@ static char *litbufdup(void);
 static void addlit(char *ytext, int yleng);
 static void addlitchar(unsigned char ychar);
 
+/* LCOV_EXCL_START */
+
 %}
 
 %option 8bit
@@ -186,6 +188,7 @@ WAIT				{ return K_WAIT; }
 				}
 %%
 
+/* LCOV_EXCL_STOP */
 
 static void
 startlit(void)

src/backend/replication/syncrep_scanner.l

@@ -32,6 +32,8 @@ static YY_BUFFER_STATE scanbufhandle;
 
 static StringInfoData xdbuf;
 
+/* LCOV_EXCL_START */
+
 %}
 
 %option 8bit
@@ -112,6 +114,7 @@ xdinside		[^"]+
 .			{ return JUNK; }
 %%
 
+/* LCOV_EXCL_STOP */
 
 /* Needs to be here for access to yytext */
 void

src/backend/utils/misc/guc-file.l

@@ -57,6 +57,8 @@ static void record_config_file_error(const char *errmsg,
 static int	GUC_flex_fatal(const char *msg);
 static char *GUC_scanstr(const char *s);
 
+/* LCOV_EXCL_START */
+
 %}
 
 %option 8bit
@@ -107,7 +109,7 @@ STRING			\'([^'\\\n]|\\.|\'\')*\'
 
 %%
 
-
+/* LCOV_EXCL_STOP */
 
 /*
  * Exported function to read and process the configuration file. The