Better warning in case of `@form`

When having a problem like:
```
/** \file */

/**
 * The fie
 *
 * @form: the new format
 * @content: the content of the form
 *
 * Sets @form content to be @content.
 *
 * \f$ \alpha \f$ \f[ \beta \f]
 */
void fie(char *form, char *content);
```
we get warnings like:
```
.../aa.h:5: warning: Wrong formula id -1
.../aa.h:6: warning: Found unknown command '\content'
.../aa.h:8: warning: Wrong formula id -1
.../aa.h:8: warning: Found unknown command '\content'
```

The `@form:` is in RST analogue to the doxygen `@param form` but not understood by doxygen.
The result is that it is seen as an formula as doxygen translates the formula commands to `\form`.
For `@content` is handled properly as this is not a doxygen command.

In this patch a more unique name is chosen so these type of conflicts don't appear (that easy). The resulting, better, warnings are now:
```
.../aa.h:5: warning: Found unknown command '\form'
.../aa.h:6: warning: Found unknown command '\content'
.../aa.h:8: warning: Found unknown command '\form'
.../aa.h:8: warning: Found unknown command '\content'
```

1 files changed, 3 insertions, 3 deletions

diff --git a/src/doctokenizer.l b/src/doctokenizer.l
index 22b14a0..caa8b35 100644
--- a/src/doctokenizer.l
+++ b/src/doctokenizer.l
@@ -363,7 +363,7 @@ LINKMASK  [^ \t\n\r\\@<&${}]+("("[^\n)]*")")?({BLANK}*("const"|"volatile"){BLANK
 VERBATIM  "verbatim"{BLANK}*
 SPCMD1    {CMD}([a-z_A-Z][a-z_A-Z0-9]*|{VERBATIM}|"--"|"---")
 SPCMD2    {CMD}[\\@<>&$#%~".+=|-]
-SPCMD3    {CMD}form#[0-9]+
+SPCMD3    {CMD}_fakeform#[0-9]+
 SPCMD4    {CMD}"::"
 SPCMD5    {CMD}":"
 INOUT	  "inout"|"in"|"out"|("in"{BLANK}*","{BLANK}*"out")|("out"{BLANK}*","{BLANK}*"in")
@@ -578,9 +578,9 @@ REFWORD_NOCV   {FILEMASK}|{LABELID}|{REFWORD2_NOCV}|{REFWORD3}|{REFWORD4_NOCV}
                              yylineno++; 
   		          }
 <St_Para>{SPCMD3}      {
-  			 g_token->name = "form";
+  			 g_token->name = "_fakeform";
 			 bool ok;
-			 g_token->id = QCString(yytext).right((int)yyleng-6).toInt(&ok);
+			 g_token->id = QCString(yytext).right((int)yyleng-11).toInt(&ok);
 			 ASSERT(ok);
 			 return TK_COMMAND_SEL();
   		       }