[DOC] Improve LangRef description of declare

[speryt]

Summary

This patch fixes formatting inside Functions section of declare
by making it consistent with the way how define is written.

Fixes #39844

[RKSimon]

LGTM - but maybe commit the define move seperately from the declare addition?

[speryt]

Following @RKSimon suggestion I've split diff on two separate diffs.

[speryt]

Refactor of Functions added in D125831.

[speryt]

@RKSimon could you please merge this diff? I don't have required permissions to do so. Thanks!

llvm/docs/LangRef.rst

 optional :ref:`linkage type <linkage>`, an optional :ref:`runtime preemption
 specifier <runtime_preemption_model>`,  an optional :ref:`visibility
 style <visibility>`, an optional :ref:`DLL storage class <dllstorageclass>`,
 an optional :ref:`calling convention <callingconv>`,
 an optional ``unnamed_addr`` attribute, a return type, an optional
 :ref:`parameter attribute <paramattrs>` for the return type, a function
 name, a (possibly empty) argument list (each with optional :ref:`parameter
 attributes <paramattrs>`), optional :ref:`function attributes <fnattrs>`,
-an optional address space, an optional section, an optional alignment,
-an optional :ref:`comdat <langref_comdats>`,
+an optional address space, an optional section, an optional partition,
+an optional alignment, an optional :ref:`comdat <langref_comdats>`,
 an optional :ref:`garbage collector name <gc>`, an optional :ref:`prefix <prefixdata>`,
 an optional :ref:`prologue <prologuedata>`,
 an optional :ref:`personality <personalityfn>`,
 an optional list of attached :ref:`metadata <metadata>`,
 an opening curly brace, a list of basic blocks, and a closing curly brace.
 
+Syntax::
+
+    define [linkage] [PreemptionSpecifier] [visibility] [DLLStorageClass]
+           [cconv] [ret attrs]
+           <ResultType> @<FunctionName> ([argument list])
+           [(unnamed_addr|local_unnamed_addr)] [AddrSpace] [fn Attrs]
+           [section "name"] [partition "name"] [comdat [($name)]] [align N]
+           [gc] [prefix Constant] [prologue Constant] [personality Constant]
+           (!name !N)* { ... }
+
+The argument list is a comma separated sequence of arguments where each
+argument is of the following form:
+
+Syntax::
+
+   <type> [parameter Attrs] [name]
+
 LLVM function declarations consist of the "``declare``" keyword, an
 optional :ref:`linkage type <linkage>`, an optional :ref:`visibility style
 <visibility>`, an optional :ref:`DLL storage class <dllstorageclass>`, an
 optional :ref:`calling convention <callingconv>`, an optional ``unnamed_addr``
 or ``local_unnamed_addr`` attribute, an optional address space, a return type,
 an optional :ref:`parameter attribute <paramattrs>` for the return type, a function name, a possibly
 empty list of arguments, an optional alignment, an optional :ref:`garbage
 collector name <gc>`, an optional :ref:`prefix <prefixdata>`, and an optional
 :ref:`prologue <prologuedata>`.
 
+Syntax::
+
+    declare [linkage] [visibility] [DLLStorageClass]
+            [cconv] [ret attrs]
+            <ResultType> @<FunctionName> ([argument list])
+            [(unnamed_addr|local_unnamed_addr)] [align N] [gc]
+            [prefix Constant] [prologue Constant]
+
 A function definition contains a list of basic blocks, forming the CFG (Control
 Flow Graph) for the function. Each basic block may optionally start with a label
 (giving the basic block a symbol table entry), contains a list of instructions,
 and ends with a :ref:`terminator <terminators>` instruction (such as a branch or
 function return). If an explicit label name is not provided, a block is assigned
 an implicit numbered label, using the next value from the same counter as used
 for unnamed temporaries (:ref:`see above<identifiers>`). For example, if a
 function entry block does not have an explicit label, it will be assigned label

 be significant and two identical functions can be merged.
 
 If the ``local_unnamed_addr`` attribute is given, the address is known to
 not be significant within the module.
 
 If an explicit address space is not given, it will default to the program
 address space from the :ref:`datalayout string<langref_datalayout>`.
 
-Syntax::
-
-    define [linkage] [PreemptionSpecifier] [visibility] [DLLStorageClass]
-           [cconv] [ret attrs]
-           <ResultType> @<FunctionName> ([argument list])
-           [(unnamed_addr|local_unnamed_addr)] [AddrSpace] [fn Attrs]
-           [section "name"] [partition "name"] [comdat [($name)]] [align N]
-           [gc] [prefix Constant] [prologue Constant] [personality Constant]
-           (!name !N)* { ... }
-
-The argument list is a comma separated sequence of arguments where each
-argument is of the following form:
-
-Syntax::
-
-   <type> [parameter Attrs] [name]
-
-
 .. _langref_aliases:
 
 Aliases
 -------
 
 Aliases, unlike function or variables, don't create any new data. They
 are just a new symbol and metadata for an existing position.